The Lake Washington Ship Canal, which runs through Seattle, Washington connecting Lake Washington to Puget Sound, is a system consisting of, from east to west, Union Bay, the Montlake Cut, Portage Bay, Lake Union, the Fremont Cut, Salmon Bay, the Hiram M. Chittenden Locks, and Shilshole Bay. Started in 1911, the canal was officially completed in 1934, though the Locks had officially opened 17 years earlier.

As early as 1854 there had been talk of building a navigable connection between the two bodies of water. 13 years later the U.S. Navy gave its endorsement to this idea, with a view to possibly building the Puget Sound Naval Shipyard on Lake Washington, but nothing was built in time to prevent their placing it at Bremerton, on the other side of the Sound, instead.

In 1891 the U.S. Army Corps of Engineers gave its backing to the project. Some preliminary work began in 1906, and work began in earnest five years later. In 1916 the water level of Lake Washington dropped by nearly nine feet (3 m) when the Montlake Cut was completed, replacing the Black River as the lake's outlet in favor of Portage Bay and Lake Union. With the opening of the Locks on May 8, 1917, there was finally a navigable passage from the lake to the sound.

The Canal's crossings, from east to west, are the Montlake Bridge carrying Montlake Boulevard over the Montlake Cut, the University Bridge carrying Eastlake Avenue over Portage Bay, the Ship Canal Bridge carrying Interstate 5 over Portage Bay, the George Washington Memorial Bridge (commonly called the Aurora Bridge) carrying Aurora Avenue (Washington State Route 99) over the west end of Lake Union, the Fremont Bridge connecting 4th Avenue to Fremont Avenue over the Fremont Cut, the Ballard Bridge carrying 15th Avenue over Salmon Bay, and the Burlington Northern Santa Fe Railway's Salmon Bay Bridge over Salmon Bay.