The Mississippi and Illinois Rivers, Arteries of a Continent

Illinois is defined, on its west and south, by two of the great rivers of North America. The Mississippi runs the entire western border of the state, from the Wisconsin line north of Galena all the way down to Cairo at the southern tip, where it meets the Ohio. The Illinois River, formed southwest of Joliet where the Kankakee and Des Plaines meet, cuts diagonally southwest for two hundred and seventy miles before joining the Mississippi at Grafton, just upstream from where the Missouri comes in from the west. Standing at Grafton, you are at the junction of three major river systems, a point of confluence that Native peoples recognized for millennia before any European arrived.

For three centuries, these rivers were the highways of the interior. The French moved fur south on the Illinois and into the Mississippi. Spanish flatboats came upstream from New Orleans with manufactured goods. American settlers floated down from Pittsburgh and Cincinnati on keelboats and flatboats, bringing livestock, tools, and families. The Mississippi steamboat era, running roughly from the eighteen twenties through the Civil War, made cities like Alton, Quincy, and Galena wealthy and connected Illinois commerce to the entire continent south to the Gulf.

The rivers also flooded. The Illinois River valley has some of the most extensive floodplain forests and backwater lakes in the Midwest, the remnant of a landscape that once covered millions of acres. Drainage projects and levee construction in the twentieth century transformed most of the floodplain into farmland, but the river still swells in spring, and the fish and waterfowl that use the Illinois valley flyway travel a corridor that has not fundamentally changed since the Pleistocene.