top of page

The Illinois River Bluffs

An Inventory of the Region's Resources

Illinois Department of Natural Resources


For other reports in this series, click here

The Illinois River Bluffs—watered by the state's namesake river and home to Peoria, the quintessential Midwestern city—can be considered the heart of Illinois in more than the geographical sense. As defined here, the Illinois River Bluffs begins near Hennepin, where the Illinois River makes its "Big Bend" toward the south, and ends at the southern end of Peoria Lake at East Peoria. The several tributaries of this stretch of the river—Senachwine Creek, Crow Creek West, Crow Creek East, Clear Creek, Sandy Creek, and others—drain nearly 561,000 acres in west central Illinois. The area includes most of Marshall and Woodford counties as well as small portions of Stark, Bureau, La Salle, Tazewell, Putnam, and Peoria counties.


This part of Illinois marks the furthest reach of the massive glaciers that crept from the north and east during the most recent ice age. As the ice walls melted, rock rubble piled up along their edges. The resulting moraines snake across today's landscape, running roughly north to south for dozens of miles. The bigger ones are a mile or two wide and stand as much as 100 feet above the surrounding land. Borne of water, the moraines were also vulnerable to it; streams sliced through them on their way from the uplands to the Illinois River below. The resulting picturesque terrain belies central Illinois's reputation for topographical dullness.


Generally speaking, the more rugged the local terrain, the more varied will be the plants and animals that find refuge in its nooks and crannies. Although much has changed in the past 150 years, the Illinois River Bluffs' presettlement complexity survives here and there.


• Within a space of less than 300 acres the Miller-Anderson Woods Nature Preserve on the Bureau-Putnam county line west of Hennepin offers visitors uplands hosting old-growth oak-hickory forest and a hill prairie, ravines that are home to maple-basswood forest, and at the foot of a bluff, a sedge meadow and a seep spring.


• Sand washed onto the banks of the Illinois River by meltwaters was picked up by winds from the west and piled in dunes 20 to 40 feet tall, creating mini-environments more like central Kansas than central Illinois. Today these dunes are stable and covered with vegetation.


• Groundwater percolating through the calcium-rich rocks and gravel of moraines has created fens; unusual plant species, such as skunk cabbage and spotted phlox, which are tolerant of the resulting alkaline soils, thrive there.


• Each natural lake of the Illinois's bottomland is not one habitat but several, from seasonally-exposed mud flats to shallow water along the shore to deep water, with a distinct array of plants adapted to each.


Presettlement land changes


Because written records are scant, scientists have had to use other kinds of data to reconstruct what the Illinois River Bluffs looked like before Euro-American settlers arrived around 1820. For example, the distinctive soils that develop under wetlands remain so even when the water that formed them is drained away. Measuring the present extent of these soils, scientists estimate that wetlands—swampy forests, marshes, seeps and fens, ponds and sedge meadows—then accounted for about one acre in five.


Scientists also estimate that prior to 1820, about 32 percent of the Illinois River Bluffs region was covered with some kind of forest. Savanna—a not-quite-forest, not-quite-prairie ecosystem in which scattered large trees (usually oaks) dominate a landscape of prairie grasses and forbs—probably covered much of the land. Trees also crowded the bottomland along the Illinois, and clung to the sides of tributary ravines where they found water and shelter from prairie fires. Prairie of one sort or another covered the rest of the region.


Today the Illinois River Bluffs as a whole boasts more forest than most parts of Illinois. More than half (51 percent) of its presettlement forest area remains wooded today, compared to 31 percent statewide. More of the region's forest retains its original ecological integrity as well—0.2 percent in the Illinois River Bluffs, compared to 0.08 percent statewide.


The mix of woodland, savanna, and prairie found in the bluffs along the Illinois River is one of the largest remnant forest ecosystems left in Illinois. Critical to the ecological health of the Illinois River—among other functions, they hold the fragile surface soil against erosion—the bluffs are rich environments in their own right. They are home to flying squirrels and many birds. (Veeries nest in some woodlands, especially in the Peoria Wilds area.) The valley harbors rare plant species such as the decurrent false aster, which exists only in the Illinois River Valley and whose life cycle is adapted to the unique flooding regime found on the Illinois. The valley also serves as an essential corridor for transient species, including the federally-threatened bald eagle, the state-threatened bobcat, and many migratory bird species.


Below the bluffs in the wooded wetlands in the bottomland, brown creepers nest, as does (occasionally) the rare red-shouldered hawk. Deer, raccoon, muskrat, and mink are common. Reptiles and amphibians from the spring peeper and gray treefrog to the brown snake enliven the woods. Morels—called the Cadillac of mid-western mushrooms by Chicago Tribune outdoor writer John Husar—grow so plentifully in the Illinois River Bluffs that the second annual Illinois morel hunting championship was held at Crooked Knee Golf Course in Marshall County. There, in woodlands and meadows along a branch of Crow Creek, the winner collected more than 200 morels in two hours.


Wetlands remain a significant part of the larger Illinois River Bluffs ecosystem. In the upriver, or northern reaches of the region, wetlands are occupied mainly by forest along the main valley floors. In the downstream, or southern parts of the region, wetlands consist mainly of shallow lakes such as Upper Peoria Lake, Peoria Lake, and Goose Lake.


Some three dozen species of wetland birds are known to inhabit the region, including 16 species, such as the black-crowned night-heron and the king rail, whose survival in Illinois is officially recognized as threatened or endangered. Wetlands are also used heavily as feeding and resting places by migrant birds that move north and south across the mid-continent each spring and fall.


Many plants and animals demand highly specific habitats. Schreber's aster, a perennial member of the sunflower family, colonizes north-facing slopes of ravines. A common plant in the eastern U.S., this aster is found in Illinois only in and around the Illinois River Bluffs, and its survival in the state is considered threatened. The queen snake is found only in medium-sized creeks with rocky substrates—habitat that is rare in Illinois now that sediments have buried so many creek bottoms.


Overall, however, the Illinois River Bluffs is not a haven for rare species. Only 1.3 percent of Illinois's officially endangered species and 10.5 percent of its threatened species are found in the region. About one thousand species of vascular plants (four of five of them native) are known in the area, but only ten of them appear on the state's list of threatened or endangered (T&E) species. (This botanical catalog is thought to be incomplete by experts, who believe that the actual number of Illinois River Bluffs plant species is probably close to 1,100.) The T&E list also includes only three species of mammals, ten of birds, two of fish, and four of mussels.


While rare species are not numerous, the region boasts a number of natural communities that are rare or absent in the rest of the state. The Illinois River Bluffs contains more than half of the state's surviving good-quality glacial drift hill prairie and 47 percent of the seeps. Spring Bay Fen on the east bank of Upper Peoria Lake in Woodford County—five acres on which grow red-osier dogwood and pussy willow, along with the state-endangered showy lady's orchid and the state-threatened Queen-of-the-prairie—constitutes all the tall shrub fen in Illinois.


A survey in the 1970s by the Illinois Natural Areas Inventory (INAI) found 29 top-quality remnants of nine presettlement natural community types within the Illinois River Bluffs, most of them along the Illinois River or its tributaries, especially Senachwine Creek. (Eleven of the basin's INAI sites have been designated Illinois Nature Preserves.) In all, natural areas amount to nearly 2,500 acres, or 0.4 percent of the region's total area—quite high for central Illinois.


However, natural communities that meet the INAI's most exacting standards of ecological integrity—what are known as Category I sites—make up but 501 acres, or 0.08 percent of the region's land area. This is about the same proportion of such habitat as survives in the state as a whole.


• Of the nearly 349,000 acres of prairie thought to have been present in 1840, about 19 acres survive in high-quality condition. That consists of glacial drift hill prairie on unplow-able slopes such as those in the Wier Hill Prairie Nature Preserve overlooking Sandy Creek in Marshall County or in the Forest Park South Nature Preserve in Peoria Heights.


• Of the estimated 107,000 acres of presettlement wetlands, only about 77 acres remain as they must have appeared to the first European travelers.


• Of 181,000 acres of presettlement forest, only 401 acres survive in high-quality condition. This acreage includes 10 percent of the high quality mesic upland forest in the state.


Post-settlement changes


Euro-American farmers and builders were not the first humans to alter the landscape of the Illinois River Bluffs. Native Americans hunted to local extinction large animals such as the bison and they regularly set fire to the prairies. The rate of change accelerated after 1820 as the region was transformed into a center of agricultural, and later industrial, production. Local wetlands and prairies disappeared at about the same rate as in the rest of Illinois—of the estimated 107,000 acres of presettlement wetlands, about 33,000 acres are left—while forest and savanna disappeared at rates faster than the statewide averages. Today 60 percent of the region's land area is cropland. Another 15 percent of the land is grasslands, mostly pastures of non-native cool season grasses and ribbon-like roadside strips.


No habitat in the presettlement bluffs was richer than its riverine lakes. They included backwater lakes and "flow-through" lakes such as Goose Lake, the latter so-named because they are part of the river's main channel. (Although at a typical speed of 0.6 mph, the water in the Illinois's main channel lakes moves scarcely faster than it does in one of its stagnant backwaters.) Before settlement, the Illinois River valley floor contained so many lakes that it resembled a boundless marsh. Even today it is hard to tell exactly where one lake ends and another begins. The backwater lakes were widely drained to make farm fields, and only eleven significant backwater lakes survive along this part of the Illinois. The two kinds of lakes together make up about 50 square miles of open water, or about half (47 percent) of the present wetlands area.


The region historically supported 88 species of fish, 35 species of mussels, and 14 of malocostracans, which are large crustaceans such as crayfish. Today, the tributary streams of the Illinois River Bluffs host 53 species of fish, 6 of mussels, and 14 of malocos-tracans while the Illinois River itself hosts 82 species of fish, 33 of mussels, and 5 malocostracans. The weed shiner, a state-endangered fish known from only four locales across Illinois, used to dwell in Peoria Lake but has not been seen there since 1879. The cisco, a state-threatened fish species, was last observed in Lake Senachwine in 1935 and also is assumed by scientists to be extirpated, or locally extinct.


Between 1993 and 1995, mussel surveys in the Bluffs portion of the Illinois River found a total of 12 species; the most numerous were three species that are common across Illinois. (More systematic surveys may turn up more.) Of the four endangered or threatened mussel species that have been recorded in the region, one living mussel was found in 1971. None have been found recently.


Typical of areas along a major river like the Illinois, bird life is fairly rich. At least 275 of the 299 bird species that regularly occur in Illinois have been found in the Illinois River Bluffs. However, many of these are migrants. Only 155 of the 275 species are known to have bred here, and of the 155 breeding species, 59 are locally extinct or are only rarely present during their breeding seasons.


In general, habitat loss explains the decline in breeding birds (although some species such as the plover prefer grazed land). Plowing prairies destroyed the habitat of the upland sandpiper and that species' survival in Illinois is endangered. Among the wetland bird species that no longer breed in the Illinois River Bluffs are the American bittern, the black tern, the marsh wren, and trumpeter swan, all of which are assumed to have suffered from the draining of backwater lakes and marshes. Songbird species have been in decline across the Midwest, probably because their forest refuges are so highly fragmented. Once-safe wooded nesting areas have become easy to penetrate by predators and parasite species such as the brown-headed cowbird, which lays its eggs in the nests of songbirds. Field data from the Peoria Wilds suggests that parasitism and nest predation there are very high.


The habitat change that began 150 years ago when the prairie was broken goes on, albeit as a result of new social and economic forces—the fragmenting of once-connected habitats, competition from non-native species, the suppression of fire, urban sprawl, and the degradation of habitat by everything from grazing to off-road vehicles.


Fragmentation  Roads, fields, and houses divide forest, wetland, or prairie into habitat "islands." Isolated habitat fragments often cannot supply the resources needed by species with extensive home ranges, and severs the natural landscape links that connect disparate habitats. Also, the entire local populations of some plant and animal species in certain tracts may include only a few individuals; the smaller such local populations, the more vulnerable they usually are to disease and in-breeding stress.


The Illinois River Bluffs counts more than 700 separate emergent wetlands, land covered with water shallow enough that plants rooted in the water grow mainly above it. The largest such wetland (in the Marshall County Conservation Area near Chillicothe) is 74 acres, but the average wetland is 3.1 acres. The forested wetlands of the Illinois River Bluffs include more than 800 separate parcels with a mean size of 13.8 acres—considerably smaller than the 500 acres thought necessary to provide safe breeding habitat for many forest birds.


Exotics   Several of the plants and animals found today in the Illinois River Bluffs are not native to the region. Two percent of the bird species and 4 percent of the mammals, as well as 21 percent of the vascular plants (205 of 996 species) were introduced to the region. An example is multi-flora rose, one of 25 introduced plant species that conservationists consider invasive. Another pest is garlic mustard, which has crowded out native spring woodland wild-flowers across central Illinois. Some plants, however, because of their particular growing characteristics, have not been harmed by the newcomers. Most of the prize-winning hauls of morel mushrooms are made from stands of multiflora rose.


Fire Suppression   Fires once periodically swept the prairies and savannas of central Illinois. Started by lightning or by Native Americans, the fires were pushed by prevailing winds from west to east. Streams and ravines acted as firebreaks, protecting many groves of trees from the flames, but in open countryside the only trees to survive were mature fire-resistant species like oaks. The result was an upland landscape that had no trees at all, or a canopy of widely spaced trees amidst a grassy understory.

Fires were stopped by Euro-Americans anxious to protect their new fences and buildings. Open oak savannas quickly became overgrown with new trees, and the understory of dense woods became choked with shrubby new growth. Tree species like maples whose seedlings used to be killed off by fire survive to shade out the young of species such as oaks that need sun. Unburned oak woods thus eventually become maple woods.


Degradation  An ecosystem can be degraded by many changes, from pollution to erosion (see Erosion sidebar), altered hydrology, and grazing by livestock. Each affects the Illinois River Bluffs to some extent.


Pollution  A century ago Chicago decided to eliminate its water pollution problem by flushing it down the Illinois River. By 1922 the Illinois River at Chillicothe was dead in ecological terms. Improved sewage treatment upstream has restored that part of the river to life but not yet to health; the pondweeds, coontail, and wild celery that once sustained flocks of hungry waterfowl on Peoria Lake, for example, never came back.


Like most of Illinois, the land surface of the Illinois River Bluffs is dotted with old landfills, storage ponds, and chemically contaminated former factory sites such as the riverfront woolen mill site in Lacon. Four of these sites are severely polluted enough to merit listing among Illinois's "Superfund" sites. Some water-bearing sand and gravel deposits lie as little as 20 feet below the surface in the lowlands along the Illinois River, and their sensitivity to pollutants leached from surface sources is classed as "excessive" by state groundwater experts. Water-bearing sands underlie approximately 20 percent of the local uplands as well, but these lie somewhat deeper, making these aquifers less sensitive to contamination from the surface.


Data from air pollution monitors (located mainly in the urbanized areas in and near Peoria) show that concentrations of such common pollutants as sulfur dioxide, carbon monoxide, fine dust, and ozone have not recently exceeded the limits set to protect human health. Ongoing shifts to cleaner energy sources, changes in industrial processes, and the ongoing phase-in of tighter regulations should combine to sustain those positive trends.


For decades factories dumped long-lived toxic substances into streams and rivers where bottom-feeding fish continue to ingest them. Because of this, state officials have issued a fish consumption advisory for channel catfish 15 inches and larger taken from the Illinois River above the dam at Peoria. More than 75 percent of the land area of stream sub-basins such as Sandy Creek and the north and south branches of Crow Creek East are planted in row crops. Surface waters in such areas are susceptible to runoff from fields carrying sediments, fertilizers, and pesticides.


Altered hydrology   Draining chronically wet soils makes them farmable, but it destroys some kinds of habitat and alters the way others function. While some amphibians adapt well to humanized environments—the bullfrog can use drainage ditches, flooded fields, even livestock watering troughs as breeding habitat—most species are not so opportunistic. The wet prairies preferred by the eastern massasauga snake have been dramatically reduced in extent since settlement, with the result that the snake has been extirpated from the Illinois River Bluffs.


After a heavy rain or snow melt, storm drains, ditches and drainage pipes carry water to nearby streams faster than the water could percolate to them through the soil. Flood "pulses" in streams whose watersheds are artificially drained thus peak sooner and higher than if the water had moved into the stream naturally, boosting the water's erosive energy and the potential for flooding downstream. Undrained soils act as a reservoir from which water migrates into adjacent streams in dry months. Drainage systems divert water from this reservoir, making nearby streams tend to run lower (and run low longer) than normal.


This is a problem for barge operators on the Illinois. Dams to stabilize water levels for navigation were among the first major alterations made to the natural Illinois River. After a lock was built at Henry in 1872, locals boasted that it was "the best town in Illinois by a dam site." Between 1919 and 1939 new and bigger dams deepened the river channel to nine feet, but also interrupted seasonal fluctuations in water levels on which plants (and thus animals) had come to depend.


Degraded habitats are not dead, however altered they may be. "Cultural" habitats like towns or cropland are anything but pristine in ecological terms, but they support many species of plants and animals. Many of these are not natives but newcomers that have long been adapted to similar habitats in other parts of the world. Of some two dozen cropland bird species in the Illinois River Bluffs, the most numerous by far are introduced species such as the house sparrow, rock dove or feral pigeon, European starling, and ring-necked pheasant. Some native species also adapt well to humanized environments. Wood duck, kestrels, and nighthawks, for example, are among more than a dozen bird species that nest in chimneys and on roofs.


Because the Illinois River Bluffs is so extensively humanized, the ways people manage land can have big impacts on wildlife. For example, in the 1950s farmers began plowing their harvested corn fields in the fall; this sharply decreased waste grain available to field-feeding mallards as they migrated through central Illinois. In the 1980s, much farmland of marginal quality was taken out of production and planted in soil-conserving grasses and other groundcover under terms of a federal conservation program; this boosted the amount of habitat for grassland birds.


Human uses


Apart from its fertile soils, the Illinois River Bluffs has few mineral resources. Currently sand and gravel left by glaciers are mined from 10 active pits along the banks of the Illinois River. At the turn of the century former farm towns like Sparland boomed when coal mines opened. But, while coal remains plentiful, its thinness and chemical composition make it commercially unattractive in today's market, and there is no active mining at present.


When hunters think of the Illinois River Bluffs they think of ducks. Several species of ducks, including mallards, stop at the region's backwater lakes on their annual migration. The river was a famous shooting grounds as early as the 1880s. (One of the first hunt clubs in Illinois was formed by Peoria area businessmen in 1886.) Sportsmen from across the Midwest sustained a modest tourism infrastructure. Henry is only one of what one historian described as "the several river towns that have claimed to be the duck-hunting capital of the world." In Sparland, the Whiffle Tree House (a residence turned into a lodge) became popular with visiting duck hunters from Chicago—the clientele was rumored to include celebrities such as Al Capone and Joe Louis.


What began as a private privilege became a public service. The 2,900-acre Woodford County Conservation Area was originally known as the Woodford Public Shooting Grounds. It is one of two major recreation areas owned and maintained by the State of Illinois along the Illinois River and at Goose Lake, one of the largest backwater lakes left on the river. The other is the 6,000-acre Marshall State Fish and Wildlife Area, made up of three separate parcels of land along both banks of the Illinois River in Marshall and Peoria counties. Migrating waterfowl stop here to rest, and wood ducks nest here all year round. Together these sites offer nearly 9,000 acres for fishing, boating, camping, hunting, hiking, and wildlife viewing, and generate an estimated $1.3 million in total economic output to the area.


Hunting remains popular measured by purchases of hunting licenses. Waterfowl, deer and squirrel are the most popular game. Lake Senachwine is a prime area for duck and geese hunting. Attendance at the Marshall State Fish and Wildlife Area dropped from nearly 84,000 in 1976 to a low of 54,000 in 1980, but since 1981 the number of visits has slowly rebounded, to more than 71,000 in 1996. Hunters there in 1997 averaged more than 1.5 ducks per day, a success rate that ranks among the seven highest among Illinois's public hunting areas. Recent improvements in duck habitat suggest that area hotels and restaurants might again host large numbers of hunters, anglers, and other wildlife enthusiasts traveling from outside the region.


As one would expect in an area with so much open water, pleasure boating is popular among the people of the Illinois River Bluffs. Marshall County includes 73 registered boat owners for every 1,000 residents, 16th highest among Illinois's 102 counties. Thanks to improved water quality, sport fishing has improved compared to 20 years ago. The Illinois River at the Marshall State Fish and Wildlife Area is an especially good spot for channel catfish, and the Peoria area has become the site of largemouth bass fishing tournaments. The Woodford County Conservation Area offers anglers 3,500 feet of man-made channels that provide excellent bullhead and crappie fishing in the late winter and early spring, when warm water from artesian wells keep the channels free from ice.


In addition to traditional rural recreation, activities such as picnicking and camping are growing in popularity, as are nature- and fitness-oriented pastimes like hiking, birding, and wildlife watching. As many as 75 great blue herons at one time can be spotted fishing in the shallow waters of some backwaters of the Illinois. During winter bald eagles soar above the frozen lakes or perch atop snags—sights that increasingly draw a crowd. Hawks, woodpeckers, and owls, especially barred owls, are common to the area. Wood ducks and Canada geese commonly nest and raise their young at the Woodford County Conservation Area, and at the Marshall State Fish and Wildlife Area beaver dams dot the backwaters.


Agriculture  The Illinois River Bluffs, like most of central Illinois, is uniquely blessed by nature for farming. Away from the stream valleys the terrain is mostly flat, and the region has a continental climate that is wettish in spring and summer when growing plants need rain. Its soils developed on loess—mineral-rich dustlike rock debris left behind by melting glaciers—that was spread by winds into a blanket several feet deep in places.


While farming remains a major industry in Woodford and Marshall counties, it no longer is the major industry. In 1970, the farm sector led the Marshall County economy in employment and earnings; by 1994 it was fourth in both. In Woodford County the farm sector declined 20 percent in relative economic importance in the past 20 years or so. Farm jobs have become fewer as the number of farms dropped 20 percent between 1978 and 1992, mainly as a result of increasing average farm size. (Total farm acres shrank, too, but only by 6 percent.) Farm cash receipts fluctuate with weather and crop prices, but over recent years the general trend has been downward.


Urbanization  In 1830, the Native American chief Senachwine is said to have told his council: "The white men of the east . . . will overrun and take possession of this country. They will build wigwams and villages all over the land . . . . " In parts of the Illinois River Bluffs, this prophecy is coming true. Once-remote farms have acquired new value as building sites. Peoria, the economic engine of the region, has bounced back from the dark days of the 1980s. New industries are locating farther afield on Peoria's periphery; major businesses with 250 or more employees operate in Toluca, Henry, Mossville, and Goodfield.


Woodford County is part of the Tri-County Peoria metropolitan area (with Peoria and Tazewell counties) that is home to roughly 350,000 people. Woodford County (mainly its southwest corner) has grown 70 percent since World War II. Indeed Woodford is expected to lead the area in the rate of jobs and population growth over the next 20 years. New developments are springing up, like Kentshire Estates in the Woodford County town of Metamora, where houses sell for a third of a million dollars. Another symptom of this outward migration is the recent expansion of shopping along Illinois Route 116, where country-dwellers now have access to the apparatus of urban life, from sports bars and car dealerships to a health club and a video store.


Urban development is also occurring north of Peoria in Peoria County. It has already impacted some of the best remaining natural areas in the state, and threatens others as it sprawls northward. One of the proposed Peoria-Chicago highway routes would slice right through the bluffs.


Even so, population growth has not put as much pressure on the natural resources of this region as it has on, say, northeast Illinois. Humans, no less than other animals, migrate in search of resources needed to live, a fact reflected in population shifts in the past 120 years. Economic downturns and job losses in Peoria County in the 1980s prompted ten percent of the people to leave. Overall, since 1870 the area has grown at half the rate as the state as a whole. Even in suburbanizing Woodford County urban uses in 1990 took up less than three percent of the land area, and "urban" dwellers constituted only about one in five residents. Marshall County, more distant from and with poorer road access to job centers, has endured the same sort of population stagnation that has stymied most of Illinois's remoter rural counties, and has 25 percent fewer people than in 1870.


Protecting the land


One hundred and fifty years of Euro-American habitation has not destroyed nature in the Illinois River Bluffs, but most of its natural systems are less diverse than they were. Some of these simplified habitats may be restored to something closer to their presettlement complexity by informed human intervention.


For example, while few other wooded tracts in the area are large enough to provide optimum breeding habitat for forest birds, the Peoria Wilds, combined with wetlands in Marshall County, could turn the Illinois River Bluffs into a breeding source for other parts of Illinois. Studies suggest that prescribed fires can benefit bird species such as the northern oriole, summer tanager, rose-breasted grosbeak, and great crested flycatcher. The red-headed woodpecker, whose presence in the Midwest has declined nearly two percent a year since 1966, has also shown higher reproductive success in burned woods. The region also could be made more welcoming to migrant birds that seek open woods by restoring the Illinois River Bluffs' degraded but still viable savanna.


Similarly, the region may serve as a useful dispersal route for bobcats moving through it from other places. A bobcat was sighted in 1994 in Singing Woods, four miles north of Peoria. Bobcats are a stern test of eco-management because the cats require extensive and varied terrain and cover. It needs to be determined if the area offers forested tracts large enough to support a local population.


The Illinois River Bluffs in many ways is a perfect laboratory for experiments in large-scale ecological enhancement. Its natural centerpiece, the Illinois River, resides entirely within one state, so restoration efforts will not be compromised by interstate disputes over priorities and methods. A blurry "before" snapshot of the presettlement Illinois River Bluffs can guide restoration. The snapshot is a century's worth of field data collected by pioneer ecologists such as Dr. Stephen A. Forbes, a former chief of the Illinois Natural History Survey and one of the fathers of the study of ecology. Large ecosystems as rich in data as they are in habitats are rare. This is one reason why the Illinois River was one of three river-flood-plain ecosystems in the U.S. to be given priority for restoration by the National Academy of Science National Research Council.

Since the 1970s public and private agencies—among them the State of Illinois departments of Agriculture and Natural Resources, local Soil and Water Conservation Districts, The Nature Conservancy, and assorted federal pollution control, conservation,  and farm agencies—have initiated programs in the region. Their purposes variously are to create wildlife habitat, stem erosion, set aside wetlands, or keep sediment-laden water out of the floodplain. Such efforts are often underfunded and uncoordinated. For example, different riverine lakes are managed by different public agencies, from different levels of government, having different agendas and using different techniques.


Nevertheless, environmental enhancement efforts have had a positive cumulative impact. The double-crested cormorant has begun to recolonize former breeding areas around the edges of some of the Illinois River's larger backwater lakes, and the wild turkey again roams the woods of the Illinois River Bluffs.


As more is attempted, more can be learned. By the 1990s, ecological restoration was being considered on an ever-wider scale and with increasing ecological sophistication. Several projects aim to restore the structure and function of the Illinois River floodplain, which should enhance habitat for some waterfowl, wading and shorebirds. (The benefits for other types—marsh birds, passerine or perching birds—are not yet as certain.) The U.S. Fish and Wildlife Service is using historical records of the pristine Illinois River as a guide to simulate nature's flood cycle at the Cameron-Billsbach Unit of the Chautauqua National Wildlife Refuge in Marshall County, where levees are being set back from the river to increase floodplain area and banks are being stabilized using native plants.


Restoring natural systems on this scale is an evolving art. Restored prairies usually are species-poor for years, dominated by a few warm-season grasses. Restoring the function of wetlands is a challenging bit of hydrological engineering; building nature's biological complexity into an artificial wetland is much harder to do. Stopping grazing slows the spread of invasive plants in wooded under-stories, but complete restoration of presettlement forest plant communities apparently takes years of active intervention, usually including regular fires (which most native species are adapted to survive) and replanting displaced native species.


The economic, social, and political challenges to restoration on a regional scale are even more daunting. The human system of land ownership and controls nearly matches in complexity the natural system it overlays. Currently, 11,300 acres are in state ownership, and 1,622 in federal ownership. In addition there are 11 Illinois Nature Preserves within the Illinois River Bluffs, composing 1,300 acres, most of them fragments of once-larger natural communities. Not all the nature preserves are publicly owned, but because of their status they enjoy the same legal protections as publicly-owned sites.


While significant ecologically, these parcels constitute only a minute fraction of the region's land area. Many local INAI sites—each potentially deserving of nature preserve status—are on private land, where even species that are officially listed as endangered or threatened are not protected by law. The thousands of acres that, while not of prime ecological quality, might be managed in ways that reduce soil loss, increase habitat for huntable birds, or buffer natural areas are also in private hands.


Achieving large public purposes in an environment that is privately owned led in 1997 to the adoption of  an Integrated Management Plan for the Illinois River, including the Illinois River Bluffs. The plan was a result of a volunteer valley-wide planning effort that began in 1994. Farm, conservation, and local business leaders took part.


The plan's aim is to restore a naturally diverse valley that is sustained by natural ecological processes and is managed to support compatible social and economic activities. More specifically, the plan calls for local people to manage water levels to reduce flood crests and control sedimentation; protect, restore and expand critical habitats whose health is vital to the ecological health of the river; provide landowners who want it with cost-sharing and technical help in setting up conservation practices; reduce pollution from city-owned sewer systems; and reduce erosion from nonfarm lands and streambanks.


The people who drafted the Integrated Management Plan agreed that their work would be based on such key principles as respect for private property, voluntary grassroots involvement, and coordination among governments. Typical of the new approach is the restoration work of the Peoria Park District's Peoria Wilds project. The oak-hickory woodlands and hillside prairies owned by the district are bordered by private homes whose backyards often contain valuable natural plant communities. Cooperating state, local and non-profit agencies and volunteers work with the private landowners who wish to protect and restore these natural communities.


Can community groups, landowners, and municipal, not-for-profit, state, and federal agencies work together to protect and restore a large and significant natural system that is in both public and private hands? The attempt will require not just a new relationship between people and nature, but between people and people. No one management approach will perfectly satisfy all uses, and compromises will be required of all parties to the process. The result may be an Illinois River Bluffs that is neither perfectly natural nor perfectly human, but a better place for each. ●


Sidebar: Valley geology


Just as the Illinois River Bluffs is the heart of Illinois, the Illinois River is the heart of the Illinois River Bluffs. While not a fabled stream like the Hudson or the Columbia or the nearby Mississippi, it is Illinois's grandest natural landmark.


In places along the middle Illinois, such as just south of Chillicothe, the floodplain stretches seven miles from one bluff to the other. The curious tourist is entitled to wonder how a stream as placid as today's Illinois River managed to cut for itself such an imposing valley. The Illinois is no Colorado River, gnawing away at the earth like a hungry dog on a bone. The land drops a mere 21 feet in the more than 200 miles from the head of the Illinois River to where the Illinois empties into the Mississippi. The river has so little energy that it cannot even carry away all the sediments dumped into it by its

tributaries, much less clean the valley of sediments accumulated through a long and muddy past. Where most rivers dig themselves ever deeper into the earth, the Illinois is lifting its bed higher and higher as sediments pile up, giving new meaning to the phrase, "the river is rising."


How then did the Illinois River carve such a great gash in the ground? It didn't. The ancient Mississippi once flowed through what is today the Illinois River Bluffs. The most recent of the great ice sheets that crept into central Illinois from 22,000 to 12,500 B.C. obliterated the great river's course, pushing it west into its present course. The Illinois was born later, a child of meltwaters that cut a new channel—the present upper Illinois valley—across northeast Illinois to Hennepin. There the gushing waters met the old river's bed, which it slipped into like a child in her daddy's shoes.


Erosion is perfectly natural. In fact, today's Illinois River Bluffs landscape consists of rocks that were worn down by water and moved there from other places. These glacial deposits are imposing in mass but yield easily to the power of water to dislodge and carry them away piece by piece. Neither the region's loess-covered surface or its subsoils (unconsolidated jumbles of gravel, stones, and clays) offer much resistance to moving water. Slopes here are steep by central Illinois standards. The uplands west of the Illinois River drop nearly 500 feet to the river's edge. Some streams west of the river fall nearly 20 feet per mile from their headwaters, which boosts the speed of their waters and thus their power to slice through bottoms and banks.


Usually, erosion's rearranging of the landscape is fairly steady, and natural communities adjust to it. But humans in recent centuries have sped up erosion by stripping much of the landscape of its protective plant cover. Parts of the middle Illinois River valley, including the Illinois River Bluffs, have lost seven of the original 13 inches of topsoil in a mere 150 years.


In central Illinois the rains tend to fall heaviest at the time of year—spring—when the fields are most vulnerable to their pummeling. When Richland Creek is running low, for example, sediment concentrations are two milligrams per liter of water; during a typical month of May, the concentration of sediments rise to more than 8,200 mg/l.

Sediments are less concentrated in the Illinois River itself. (A typical recent reading at Chillicothe is 490 mg/l.) But because of its much greater water volume, the Illinois's total sediment load is impressive. When the river runs muddy, it can carry an estimated 93,800 tons of soil per day past any one point.


Thus, the region's greatest resource, its soils, is also its most troublesome problem. Sediment washed into streams and lakes reduces the water-holding capacity of the flood-plain, and thus its ability to absorb floodwaters. It also clogs the Illinois River channel, which must be dredged to permit continued navigation by barges, an ongoing and expensive chore.


Sedimentation also fouls water. Suspended soil particles make water too murky for predatory fish to see their prey. Sediment blankets stream bottoms, burying fish nesting sites and making it hard for plants to take root.


Because so much Illinois River Bluffs land is agricultural, farm fields are the source of most eroded soil, even when soil losses per acre are modest compared to construction sites or stream banks. Crops planted in rows leave more of a field's surface exposed, and since the 1920s intensive row crop production of corn and soybeans has almost doubled in the area. In recent years, however, soil movement has slowed, thanks to farmers adopting practices such as "no-till" cultivation and withdrawing highly erodible marginal lands from production.


While erosion is no longer the crisis it was in the 1970s, soil movement remains a problem. The Illinois River's faster-running tributaries are more efficient at creating silt than the big river is at carrying it away. Soil removed from the river's large watershed is funneled into relatively small floodplain lakes. Their appearance notwithstanding, many of the backwater lakes in the Illinois River Bluffs are more land than lake. The average depth of Upper Peoria Lake has gone from 7.6 feet in 1903 to 5.3 feet today; in Peoria Lake, the change has been from 8.0 feet to 2.6. Current sedimentation rates, if unchecked, will eventually fill half the remaining volume of many Illinois River lakes within 200 years or less. ●


Sidebar: Disappearing ducks


The Illinois today is a working river mainly for barge crews. For many decades, however, the river provided a living for mussel fishermen, fishermen, ice cutters, and commercial hunters whose incomes were the economic base of scores of small communities. In 1908, the river yielded nearly 24 million pounds of fish, enough to support 2,500 commercial fishermen. Markets for shell kept 2,600 mussel boats busy. Hunters descended on river hamlets in flocks each fall like the ducks and geese they coveted, providing seasonal income for many a farmer happy to rent out fields.


Then occurred what was the single gravest ecological disaster in Illinois history, or rather a series of disasters. First, at the turn of the present century the Chicago Sanitary and Ship Canal opened, diverting water from Lake Michigan into the Illinois via the Chicago River, leaving the Illinois in what amounted to a permanent flood. Low-water levels at Peoria rose five to six feet after diversion began in 1900, flooding and eventually killing thousands of acres of bottomland forest. Worse, untreated sewage was flushed downstream from the big city. The decomposing sewage fed uncountable bacteria, which in turn consumed oxygen dissolved in the water. By 1923 the river's water was starved of vital oxygen as far downriver as Peoria.


Injury was added to insult beginning in 1919, when a series of dams were built to provide a dependable nine-foot-deep channel for massive cargo barges. Finished in 1939, these navigation dams stopped the seasonal fluctuations in water levels to which plants and animals were adapted. Worse, dams slowed the current, and soil particles that once stayed suspended in the moving water drifted to the bottom like muddy snow.


The City of Chicago and barge companies make convincing villains in this environmental tragedy, but the citizens of the Illinois River Bluffs also had a hand in changing a biologically diverse river system into a muddy ditch. Over-fishing depleted populations of commercially desirable fish. Drainage districts formed by local farmers between 1903 and 1920 dried out thousands of acres of backwater lakes, and intensive farming of row crops from the 1950s through the 1970s pushed up erosion rates to unsustainable levels.


The combined effects of sewage dilution, higher water levels, navigation-dams, and sedimentation changes could be counted in ducks. Lesser scaups were abundant in the Illinois valley before the 1950s, especially on Upper Peoria Lake. More than 585,000 ducks were counted on one stretch of the river in 1954; three years later the number was around 10,000. Similar trends were recorded in populations of canvasbacks. Since 1948, significantly fewer migrating mallards have alighted in the Illinois valley each fall.


The main cause of the decline was a scarcity of food. The benthic macroinvertebrate community was buried by sedimentation, poisoned by pollution from factories or starved of oxygen. Small clams, snails, and other bottom-dwelling creatures disappeared, leaving diving ducks like the lesser scaup with nothing to feed on.


Also devastated were plant foods. At the turn of the century the Illinois's backwater lakes were such spectacularly fecund environments for plants that soils along the middle stretches of the river consisted of as much decayed plant matter as silt. The trees killed by rising water levels included pecans on whose nuts mallards and wood ducks feasted. (Ducks fed for years on waste grain left in harvested fields, but more efficient combines have reduced that source too.)


Sedimentation also left lake bottoms too soft for plants to root in, and aquatic vegetation that used to sustain the canvasback flocks on the Upper Peoria Lake disappeared. Tellingly, the post-1948 decline in mallard counts along the Illinois has been relatively steeper than that recorded on the larger Mississippi River, where sedimentation is less severe and has not caused such drastic reductions in the amount and variety of natural plant foods available to migrating flocks.


Changes in seasonal water level cycles hurt too. For decades moist-soil plants sprouted on thousands of acres of mud flats that appeared in mid-July and mid-September most years when the river ran low. Navigation dams stabilized water levels so that land that had usually been exposed during the growing season was flooded year around. Ironically, sedimentation has piled so deep in places that the mud flats are emerging again in late summer in spite of the higher artificial water levels—welcome news for ducks, less so for barges and pleasure boats. ●


Sidebar: Backwater lakes


During floods, when fast-running sediment-laden river water encounters still water in the side channels, the current slows. The river drops its load of sediments where river and lake meet, building up natural levees. Eventually the side channel is separated from the main channel, and a backwater lake is born. The same process that created backwater lakes dooms them. In an undisturbed river system they gradually fill up with sediment carried into them by flood water and dropped there. Deep lakes gradually become shallow, shallow lakes gradually become mud flats, mud flats gradually are colonized by willow, soft maples, and cottonwoods, and bottomland lakes gradually become bottomland forest. Meanwhile, the river busily creates new lakes in other spots.


Humans have accelerated the first process, and have interrupted the second. Existing lakes are filling in faster than in nature because of human-induced erosion in the watershed. In general backwater lakes lost 70 percent of their capacity to sedimentation since settlement. (The deposits are mostly silts and clays that are harder to remove by dredging than is sand, which is the culprit in the main channel.) And because so much of the river is leveed or drained, there are few spots at which the river can begin the process of creating new lakes to replace them.


Humans, in short, have taken nature's place as the engineer of the system. Private duck-hunting clubs de-watered certain lakes with pumps, creating mud flats on which ducks' favorite moist-soil plants can grow. Proposals have been made to use dredge spoil to create new islands or habitats behind protective berms, where the watery sediment would be able to dry out and compact. Humans will never be able to match nature's subtle engineering, but thinking like the river may improve the quality of their own. ●

To return to the main CTAP page, click here.

To return to the "Nature and environment" page,

click here.




John Hallwas

Essential for anyone interested in Illinois history and literature. Hallwas deservedly won the 2018 Lifetime Achievement Award from the Illinois State Historical Society.

Lee Sandlin Author

One of Illinois’s best, and least-known, writers of his generation. Take note in particular of The Distancers and Road to Nowhere.

Chicago Architecture Center

See Home Page/Learn/

Resources for a marvelous building database, architecture dictionary, even a city planning graphic novel. Handsome, useful—every Illinois culture website should be so good.

The Encyclopedia of Chicago


The online version of The Encyclopedia of Chicago. Crammed with thousands of topic entries, biographical sketches, maps and images, it is a reference work unmatched in Illinois.

Illinois Great Places

The Illinois chapter of the American Institute of Architects in 2018 selected 200 Great Places in Illinois that illustrate our  shared architectural culture across the entire period of human settlement in Illinois.

McLean County Museum

of History

A nationally accredited, award-winning project of the McLean County Historical Society whose holdings include more than 20,000 objects, more than 15,000 books on local history and genealogy, and boxes and boxes of historical papers and images.

Mr. Lincoln, Route 66, and Other Highlights of Lincoln, Illinois


Every Illinois town ought to have a chronicler like D. Leigh Henson, Ph.D. Not only Lincoln and the Mother road—the author’s curiosity ranges from cattle baron John Dean Gillett to novelist William Maxwell. An Illinois State Historical Society "Best Web Site of the Year."

Illinois Digital Archives


Created in 2000, the IDA is a repository for the digital collections of the Illinois State Library and other Illinois libraries and cultural institutions. The holdings include photographs, slides, and glass negatives, oral histories, newspapers, maps, and documents from manuscripts and letters to postcards,  posters, and videos.

The Illinois State Museum


The people's museum is a treasure house of science and the arts. A research institution of national reputation, the museum maintains four facilities across the state. Their collections in anthropology, fine and decorative arts, botany, zoology, geology, and  history are described here. A few museum publications can be obtained here.

Chronicling Illinois

“Chronicling Illinois” showcases some of the collections—mostly some 6,000 photographs—from the Illinois history holdings of the Abraham Lincoln Presidential Library.


I will leave it to the authors of this interesting site to describe it. "Chicagology is a study of Chicago history with a focus on the period prior to the Second World War. The purpose of the site is to document common and not so common stories about the City of Chicago as they are discovered." 

Illinois Labor History Society

The Illinois Labor History Society seeks to encourage the preservation and study of labor history materials of the Illinois region, and to arouse public interest in the profound significance of the past to the present. Offers books reviews, podcasts, research guides, and the like. 

Illinois Migration History 1850-2017

The University of Washington’s America’s Great Migrations Project has compiled migration histories  (mostly from the published and unpublished work by UW Professor of History James Gregory) for several states, including Illinois. The site also includes maps and charts and essays about the Great Migration of African Americans to the north, in which Illinois figured importantly. 

History on the Fox

An interesting resource about the history of one of Illinois’s more interesting places, the Fox Valley of Kendall County. History on the Fox is the work of Roger Matile, an amateur historian of the best sort. Matile’s site is a couple of cuts above the typical buff’s blog. (An entry on the French attempt to cash in on the trade in bison pelts runs more than

2,000 words.)




Southern Illinois University Press 2017

A work of solid history, entertainingly told.

Michael Burlingame,

author of Abraham 

Lincoln: A Life 

One of the ten best books on Illinois history I have read in a decade.

Superior Achievement Award citation, ISHS Awards, 2018

A lively and engaging study . . .  an enthralling narrative.

James Edstrom

The Annals of Iowa

A book that merits the attention of all Illinois historians

as well as local historians generally.

John Hoffman

Journal of Illinois HIstory

A model for the kind of detailed and honest history other states and regions could use.

Harold Henderson 

Midwestern Microhistory

A fine example of a resurgence of Midwest historical scholarship.

Greg Hall

Journal of the Illinois

State Historical Society

Click  here 

to read about

the book 

Click  here 

to buy the book 


Southern Illinois University Press

SIU Press is one of the four major university publishing houses in Illinois. Its catalog offers much of local interest, including biographies of Illinois political figures, the history (human and natural) and folklore of southern Illinois, the Civil War and Lincoln, and quality reprints in the Shawnee Classics series.

University of

Illinois Press

The U of I Press was founded in 1918. A search of the online catalog  (Books/Browse by subject/Illinois) will reveal more than 150 Illinois titles, books on history mostly but also butteflies, nature , painting, poetry and fiction, and more.  Of particular note are its Prairie State Books,  quality new paperback editions of worthy titles about all parts of Illinois, augmented with scholarly introductions.

University of

Chicago Press

The U of C publishing operation is the oldest (1891) and largest university press in Illinois. Its reach is international, but it has not neglected its own neighborhood. Any good Illinois library will include dozens of titles about Chicago and Illinois from Fort Dearborn to

Vivian Maier.

Northern Illinois University Press

The newest (1965) and the smallest of the university presses with an interest in Illinois, Northern Illinois University Press gave us important titles such as the standard one-volume history of the state (Biles' Illinois:
A History of the Land and Its People) and contributions to the history of Chicago, Illinois transportation, and the Civil War. Now an imprint of Cornell University Press.


Reviews and significant mentions by James Krohe Jr. of more than 50 Illinois books, arranged in alphabetical order

by book title. 


Illinois Center for the Book

Run by the Illinois State Library, The Center promotes reading, writing and author programs meant to honor the state's rich literary heritage. An affiliate of the Library of Congress’s Center for the Book, the site offers award competitions, a directory of Illinois authors, literary landmarks, and reading programs.

bottom of page