T.J. O'Brien Lock and Dam in the context of Calumet River

The Chicago Area Waterway System (CAWS) is a complex of natural and artificial waterways extending through much of the Chicago metropolitan area, covering approximately 87 miles altogether. It straddles the Chicago Portage and is the sole navigable inland link between the Great Lakes and the Mississippi River and makes up the northern end of the Illinois Waterway.

The CAWS includes various branches of the Chicago and Calumet Rivers, as well as other channels such as the North Shore Channel, Cal-Sag Channel, and Chicago Sanitary & Ship Canal. The CAWS ends near the Lockport Navigational Pool, the highest elevated of the eight pools of the Illinois Waterway. There are three major locks within the CAWS, operated by the Army Corps of Engineers: the Chicago Harbor Lock, the Lockport Lock & Dam, and the T.J. O'Brien Lock and Dam.