Class I Kaskaskia River, IL

The Kaskaskia River is the largest stream found entirely within Illinois. From its headwaters just west of Champaign to its mouth on the Mississippi River above Chester, the Kaskaskia winds its way across nearly 300 miles of central and southwestern Illinois. Its watershed (the land area draining into it) encompasses all or parts of 22 counties and about 10% of the state's total land area. (Illinois DNR)