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
Saline River (Illinois) Saline River (Illinois) The Saline River is a tributary of the Ohio River, approximately long, in the Southern Illinois region of the U.S. state of Illinois. The river drains a large section of southeast Illinois, with a drainage basin of . The major tributaries include the South Fork, Middle Fork and North Fork, all lying within the Saline Valley. The once meandering swampy river was important among Native Americans and early settlers as a source of salt from numerous salt springs where it was commercially extracted in the early 19th century. From 1807 to 1818, Illinois paid the United States