Illinois, river, 273 mi (439 km) long, formed by the confluence of the Des Plaines and Kankakee rivers, NE Ill., and flowing SW to the Mississippi at Grafton, Ill. It is an important commercial and recreational waterway. The Illinois forms the greater part of the Illinois Waterway, which links the Great Lakes with the Mississippi. The chief city on the river is Peoria.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.