Des Plaines River, river rising in Kenosha county, southeastern Wisconsin, U.S., and flowing south into Illinois through the northwestern suburbs of Chicago to Lyons. It then continues southwest past Lockport and Joliet, where it joins the Kankakee River after a course of 110 miles (177 km). The Illinois River is formed by the confluence of the Des Plaines and Kankakee rivers.
In fur-trading days the Chicago River was linked by a short portage to the Des Plaines and Mississippi rivers. In 1900 the Metropolitan Sanitary District of Greater Chicago completed a drainage canal from the south branch of the Chicago River to the Des Plaines River at Joliet, where it joined the Illinois and Michigan Canal (completed 1848). The construction of the sanitary canal reversed the flow of the Chicago River, permitting water from Lake Michigan to flow through the canal into the Des Plaines River and thence to the Illinois River. The opening of the Illinois Waterway in 1933 allowed modern barge traffic to pass between the Great Lakes and the Mississippi River.