Cal-Sag Channel

The Calumet River is a system of rivers and canals in the region between the south side of Chicago, Illinois, and the city of Gary, Indiana. Currently, the system is part of the Chicago Area Waterway System.
Historically, the Little Calumet River flowed in a broad westward arc roughly parallel to the Lake Michigan shore, then turned back east and became the Grand Calumet River, which emptied into Lake Michigan at Marquette Park in Gary. The Calumet River was a separate short stream draining Lake Calumet to Lake Michigan.
In modern times, different parts of the watershed now drain into Lake Michigan via the Indiana Harbor and Ship Canal and Burns Ditch, and into the Mississippi River watershed via the Cal-Sag Channel. The "main" Calumet River now connects to the junction of the Little and Grand Calumet Rivers, but flow is heavily restricted by the T.J. O'Brien Lock and Dam.

Source: Wikipedia https://en.wikipedia.org/wiki/Calumet_River#Cal-Sag_Channel