Project Description and Background
The lock was originally designed and built between 1936 and 1938 by the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC). The lock was constructed as a component of the historic engineering project that reversed the flow of the Chicago River to prevent river water containing sewage from flowing into the lake and contaminating the city's drinking water.
The lock chamber is 600 feet long x 80 feet wide x 22 feet deep. Filling/emptying is gravity-fed through partially opened lock gates, and there is typically a two to five-foot difference between Lake Michigan and Chicago River water levels. It takes about 12-15 minutes to cycle through the lock.
The control house was replaced in 2007 with a more modern facility, which consolidates maintenance into one building and allows for near 360-degree visibility – improving security and speeds lockages during heavy traffic periods.
In 2011, the Corps’ Chicago District completed a project to replace the structural steel sector gate leaves and associated hydraulic operating machinery. The new lock gates are designed to reduce repair and maintenance costs and prevent service disruptions. The new gates and operating machinery have fewer parts and are more reliable. They are modeled after the proven design of the Thomas J. O’Brien Lock.
The Chicago Lock is one of the busiest locks in the nation in terms of both commercial and recreational usage. On a busy day, 20-40 vessels can be locked at once. Based on the 2022 through 2025 data: the lock cycles 10,000 times during a seven month open season. The lock sees an average of 880,000 commercial passenger one-way trips and 200,000 recreational passenger one-way trips.
In 2025 there were 9,859 lockages through the chamber. Serving over 72,000 commercial, recreational, and government vessels; nearly 1.3 million passengers.
Current Status
Lock is Open April 15, 2026 through November 14, 2026
Available funds will be used for routine operations and maintenance of existing structures, including completing wall and floor repairs, switchgear and generator replacement, sector gate operating machinery repair, lock controls modernization, and selective electrical conductor replacements.
Construction activities in the lock chamber are scheduled from 16 Nov to 15 April through the 2027-2028 winter season to minimize adverse impacts to commercial and recreational users.
Check out our new Lock tutorial video!
Project Authorization
Rivers and Harbors Act of 1870, 1880, 1912, 1919, and 1962.