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
Illinois River (Colorado) Illinois River (Colorado) Illinois River is a tributary of the Michigan River, approximately long, in Jackson County in north central Colorado. It drains part of the North Park basin south of Walden. The Illinois River starts in the Never Summer Mountains near the continental divide, just south of Farview Mountain. It descends northward through a winding gorge, emerging into North Park at approximately above sea level. It flows northward through the valley as a winding stream, past Rand. It passes under State Highway 14 just southeast of Walden and joins the Michigan from the north just north of Walden. A