Lake Calumet is the largest body of water within the city of Chicago. Formerly a shallow, postglacial lake draining into Lake Michigan, it was transformed into an industrial harbor during the 20th century. Parts of the lake have been dredged, and other parts reshaped by landfill. Following the completion of the Cal-Sag Channel in 1922, which reversed the flow of the Calumet River, the lake drains into the Des Plaines River via the channel instead of Lake Michigan.

The Calumet River is a system of heavily industrialized rivers and canals in the region between the south side of Chicago, Illinois, and the city of Gary, Indiana. Historically, the Little Calumet River and the Grand Calumet River were one, the former flowing west from Indiana into Illinois, then turning back east to its mouth at Lake Michigan at Marquette Park in Gary. Now the system is part of the Chicago Area Waterway System and through the use of locks flows away from Lake Michigan to the Cal-Sag Channel.