Illinois River 20 miles (32 km) of its course, the Illinois is separated from the Mississippi River by only about five miles, by a peninsula of land that makes up Calhoun County. The Illinois joins the Mississippi near Grafton, approximately 25 miles (40 km) northwest of downtown St. Louis and about 20 miles upstream from the confluence of the Missouri River and the Mississippi. South of Hennepin, the Illinois River is following the ancient channel of the Mississippi River. The Illinoian Stage, about 300,000 to 132,000 years ago, blocked the Mississippi near Rock Island, diverting it into its present channel. After the
Embarras River (Illinois) southeastern Champaign; the southern portion of the University of Illinois campus, including the small creek near the Vet Med Building; and Meadowbrook Park in south Urbana. The Embarras flows generally southward through Douglas, Coles, Cumberland, and Jasper Counties. In Jasper County, it turns southeast for the remainder of its course through Richland, Crawford, and Lawrence Counties. Portions of the river's lower course have been straightened and channelized. It joins the Wabash River southwest of Vincennes, Indiana. Along its course, the Embarras passes the towns of Villa Grove, Camargo, Charleston, Greenup, Newton, Ste. Marie, and Lawrenceville. The United States Board on