The Thomas J. O’Brien Lock and Dam is the uppermost one on the Illinois Waterway. It is located 7 miles from Lake Michigan. It is positioned between the 130th Street Railroad Bridge and the Norfolk Southern Little Calumet Railroad Bridge.
The lock was designed by the Army Corps of Engineers. It was constructed from 1957 to 1960. It was opened in 1965. The main purpose of the lock is to regulate the flow of water from Lake Michigan into the Illinois Waterway. It has a lift of three to four feet. The lock measures 1000 X 110 feet.
The lock was named after Thomas J. O’Brien a long time Democratic congressman from the Chicago area.