Construction of the Lake Washington Ship Canal and Hiram M. Chittenden Locks was completed in 1917 by the U.S. Army Corps of Engineers. Connecting the waters of Lake Washington, Lake Union, and Salmon Bay to the tidal waters of Puget Sound, the canal and locks allow recreational and commercial vessels to travel to the docks and warehouses of Seattle's busy fresh water harbor.
The complex of locks sit in the middle of Salmon Bay and are part of Seattle's Lake Washington Ship Canal. They are known locally as the Ballard Locks after the neighborhood to their north. (Magnolia lies to the south.)
The locks and associated facilities serve three purposes:
- To maintain the water level of the fresh water Lake Washington and Lake Union at 20 to 22 feet above sea level.
- To prevent the mixing of sea water from Puget Sound with the fresh water of the lakes (saltwater intrusion).
- To move boats from the water level of the lakes to the water level of Puget Sound, and vice versa.
The complex includes two locks, a small (30 x 150 ft, 8.5 x 45.7 meter) and a large (80 x 825, 24.4 x 251.5 meter). The complex also includes a (235-foot, 71.6 meter) spillway with six (32 x 12-foot (3.7 m), 9.8 x 3.7 meter) gates to assist in water-level control. A fish ladder is integrated into the locks for migration of anadromous fish, notably salmon.
The grounds feature a visitors center, as well as the Carl S. English, Jr. Botanical Gardens.
Operated by the U.S. Army Corps of Engineers, the locks were formally opened on July 4, 1917, although the first ship passed on August 3, 1916. They were named after U.S. Army Major Hiram Martin Chittenden, the Seattle District Engineer for the Corps of Engineers from April 1906 to September 1908. They were added to the National Register of Historic Places in 1978.