T.J. O'Brien Lock and Dam

Thomas J. O’Brien Lock & Dam is a lock on the Calumet River on the south side of Chicago. The Calumet River is a tributary to the Chicago Sanitary and Ship Canal. This flows into the Des Plaines River, the Illinois River and then the Mississippi. It is 326 river miles from the Mississippi-Illinois confluence. The up river side of the dam is at Lake Michigan's level, 577 feet above sealevel. The lock dimensions are 1000' x 110' feet.