| T. J. OBrien Lock and Dam | |
|---|---|
 | |
| Location | Hegewisch, Chicago |
| Purpose | Flood control, navigation |
| Construction began | 1957 |
| Opening date | 1960 |
| Construction cost | $6,954,700 |
| Built by | Fitz Simmons & Connell Dredge & Dock Company |
| Designed by |  United States Army Corps of Engineers |
| Operator(s) | United States Army Corps of Engineers Rock Island District |
| Dam and spillways | |
| Type of dam | 4 sluice gates |
| Impounds | Calumet River to Lake Michigan harbor |
| Length | 297 feet (91 m) |
| Reservoir | |
| Normal elevation | 577 feet (176 m) above sea level |
Thomas J. O'Brien Lock & Dam is a stop lock in the Hegewisch neighborhood on the South Side of Chicago at the confluence of the Grand Calumet River and Little Calumet River, which form the Calumet River. It is a component of the Chicago Area Waterway System (CAWS), which is, itself, a part of the Illinois Waterway, which links the Mississippi River and the Great Lakes.
The Lock & Dam is named for Thomas J. O’Brien, who was a U.S. Representative for the 6th District of Illinois from 1933 to 1938 and again from 1943 to 1964.[1]