Byway Story - Geology

The Illinois River Valley as it looks today is the result of continual and often dramatic natural changes to the landscape.

Starved Rock view of Illinois RiverSome of the processes that shaped this river and its valley are, literally, as old as the hills. Sandstone and limestone bluffs recall an era, millions of years past, when an ancient sea overspread this region. The Mississippi River once flowed through this valley, before glaciers shifted its course to the west. South of Hennepin, the Illinois River follows the Mississippi's ancient channel. A more recent glacial event sculpted the upper reaches of the Illinois River. Seventeen thousand years ago, glacial melt waters burst through a rock-earth dam holding back a massive lake, unleashing the Kankakee Torrent, which carved the river valley all the way to Hennepin.

As the glaciers retreated, lichens and plants reinhabited the barren landscape, many of which sprouted from seeds left behind in the glacial deposits. In the 12,000 years since then, rich topsoils accumulated, and complex and varied communities of plants and animals-from lush bottomland hardwood forests and riparian floodplains to tallgrass prairies and woodland spring seeps-have established and flourished here.

The Illinois River Road sites below to enable you to experience how geological transformations have shaped the Illinois River Valley and how, since the end of the Ice Age, dynamic natural communities have become established in the Illinois River Valley.

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  • Fondulac Park District

    Winding high along the top of one of East Peoria’s bluffs is the scenic Fondulac Drive, a three-mile route that is owned and maintained by the Fon du Lac Park District. Nestled along the road, wh Read more [...]

  • Boggio’s Orchard

    Just outside of Granville, Illinois in the little community of Mark, Denise and Keith Boggio operate Boggio’s Little Mountain Orchard. Both children of produce marketing families, the Boggios gro Read more [...]

  • Buffalo Rock State Park

    So named because (legend has it) the area once served as a “blind canyon” where Indians ran buffalo for capture, this 298-acre park has long been a natural favorite. Much of Buffalo Rock S Read more [...]

  • Dickson Mounds Museum

    One of the major on-site archeological museums in the country, Dickson Mounds Museum also interprets the ecology of the Illinois River’s Emiquon region. The site itself lies where two major ecosy Read more [...]

  • Bradley Park

    Established in the late 19th century, the 140-acre Bradley Park is the centerpiece of Peoria’s University District. Operated by the Peoria Park District, this large park, located adjacent to Brad Read more [...]

  • McCune Sand Prairie

    This 200-acre rare prairie type was donated to the Natural Resources Conservation Service Bureau County District by Mr. and Mrs. J.D. McCune (120-acres) and the University of Illinois (80-acres). Due t Read more [...]

  • Jubilee College State Park

    Jubilee College State Park is a 3,200-acre facility situated in the Illinoisan drift-plan, replete with rolling topography and the meandering Jubilee Creek. Visitors may see deer, rabbits, squirrel, fo Read more [...]

  • Illini State Park

    Located across the Illinois River from the town of Marseilles, the 510-acre Illini State Park lies along the northern edge of the “Great Falls” of the river, where a drop in streambed grad Read more [...]

  • Robinson Park

    This wild, undeveloped 680-acre park has several narrow, informal paths that lace the site, along with a substantial segment of the better-developed Pimiteoui Trail. The park offers access to Illinois Read more [...]

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