Chicago Harbor Lock
stop lock and dam in Illinois, US
The Chicago Harbor Lock, also known as the Chicago River & Harbor Controlling Works, is a stop lock and dam located within the Chicago Harbor in Chicago, Illinois, at the mouth of the Chicago River. It is a component of the Chicago Area Waterway System, and is used to control water diversion from Lake Michigan into the river and for navigation.
History
The lock was built between 1936 and 1938 by the Sanitary District of Chicago primarily as a means of limiting diversion of water from Lake Michigan, but also as a component of the project to reverse the flow of the Chicago River to improve the water quality of the lake and for improved navigation. It 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.
In 1984, maintenance and operation of the lock was transferred to the U.S. Army Corps of Engineers, though operation of the controlling works sluice gates stayed with the Metropolitan Water Reclamation District.
Overview
The lock chamber is 600 feet (180 m) long, 80 feet (24 m) wide, and 22 feet (6.7 m) deep and can accommodate up to 100 vessels at once. It contains two pair of 30 feet (9.1 m) tall sector gates. The lock requires 12–15 minutes to cycle through a typical water-level difference of two to five feet (0.61 to 1.52 m). Water level is controlled via gravity by partially opening and closing the lock gates.
The controlling works contains eight sluice gates along its piers, each measuring 10 feet (3.0 m) x 10 feet (3.0 m), allowing water from Lake Michigan into the river for navigational and sanitation purposes during normal weather operations, and for allowing water out of the swollen river into the lake during heavy rainfall periods as a measure of last resort for flood control purposes.
This brief starts where responsible research should: with the source description of “Chicago Harbor Lock” as stop lock and dam in Illinois, US. Everything that follows is an evidence route, not borrowed authority.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Oct 23, 2025. The linked authority identifier is Q24761490. Authority coordinates are 41.888, -87.606. None of the 1 selected statements returned an explicit reference. The first chronological checks are 1936, 1938 and 1984.
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This entry incorporates text from “Chicago Harbor Lock” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.