Chicago Harbor Lock
Operated by the U.S. Army Corps of Engineers, the lock was designed and built between 1936 and 1938 by the Sanitary District of Chicago as a component of the project to reverse the flow of the Chicago River and is one of two entrances from the Great Lakes to the Chicago Area Waterway System - the other entrance being the T.J. O'Brien Lock and Dam on the Calumet River.
The lock chamber is 600 feet long, 80 feet wide, and 22 feet deep and can accommodate up to 100 vessels at once. The lock requires 12–15 minutes to cycle through a typical water-level difference of two to five feet. Water level is controlled via gravity through partially opened lock gates.
The Chicago Harbor Lock is the fourth-busiest lock in the nation for commercial use and the second-busiest in the nation for recreational use.