This past Saturday afternoon, I had the opportunity to visit the Hiram H. Chittenden Locks, also known as the Ballard Locks. They are part of Seattle's Lake Washington Ship Canal.
The website for the locks state this:
The locks serve 3 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.