The Chicago Harbor Lock separates the Chicago River from Lake Michigan. Built during the 1930s, it controls the movement of water between the Chicago River and Lake Michigan, helping maintain the reversal of the river. Able to accommodate up to 100 vessels at once, the locks are among the busiest in the nation, and are operated by the US Army Corps of Engineers. They are 600 feet long, 80 feet wide, and 22 feet deep.
