The Locks, built by the US Army Corp of Engineers in 1917, connect Lake Washington, Lake Union and Salmon Bay to the Puget Sound. They maintain the water level of the lakes at 20-22 feet above sea level and prevent the mixing of saltwater with freshwater. The visitors center provides fascinating information about this project.
The locks are in use 24/7. The grounds are open from 7am to 9pm daily. The fish ladder viewing room is open from 7am to 8:45pm.