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
Greybull River Greybull River The Greybull River is a tributary of the Big Horn River, approximately long in northern Wyoming in the United States. The river was reportedly named for a white buffalo that had been seen on its banks. Native Americans consider the appearance of a white buffalo a powerful omen. The river rises near Francs Peak in the Absaroka Mountains in the southwest corner of the Big Horn Basin. It joins with the Wood River and leaves the mountains near the town of Meeteetse, continuing through the southern parts of Park County and Big Horn County before flowing into the