<P> South of Peoria, the Illinois River goes by East Peoria and Creve Coeur, and then Pekin, Illinois, in Tazewell County, Illinois . It is then joined by the Mackinaw River and then passes through the Chautauqua National Wildlife Refuge . Across from Havana, the Illinois is joined by the Spoon River coming from Fulton County, Illinois, and across from Browning, it is joined by the Sangamon River, which passes through the state capital, Springfield, Illinois . The La Moine River flows into it approximately five miles (8 kilometers) southwest of Beardstown, which is south of Peoria and Pekin and north of Lincoln and Springfield . </P> <P> Near the confluence of the Illinois with the La Moine River, it turns south, flowing roughly parallel to the Mississippi across southwestern Illinois . Macoupin Creek joins the Illinois on the border between Greene and Jersey counties, approximately 15 miles (24 km) upstream from the confluence with the Mississippi . </P> <P> For the last 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 . </P> <P> 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 glacier melted, the Illinois River flowed into the ancient channel . The Hennepin Canal roughly follows the ancient channel of the Mississippi upstream of Rock Island . </P>

Where do the illinois and mississippi rivers meet