The Hiram M. Chittenden Locks accommodate the approximately 20-foot (6.1 m) difference in water level between Lake Washington and the sound.

As early as 1854, there was discussion of building a navigable connection between Lake Washington and Puget Sound for the purpose of transporting logs, milled lumber, and fishing vessels.

Thirteen years later, the United States Navy endorsed a canal project, which included a plan for building a naval shipyard on Lake Washington.

For centuries, people had been dragging boats between the lakes, giving names like "carry a canoe" sxWátSadweehL to the crossing points.

[7] The route directly across the narrowest part of Seattle, that is, Semple's Canal from Leschi straight across to present-day Harbor Island, was rejected in this report because of the 200 to 300 foot height of the hills that would have to be cut through.

[3] In the Rivers and Harbors Act of 1902, Congress directed the Secretary of War to appoint a committee of three officers to study the feasibility of a canal and lock system to connect Puget Sound to Lake Washington.

[9]: 26 Instead, Chittenden proposed a double concrete lock with steel gates, allowing small craft to pass with less waste.

[3][9]: 29  Though Chittenden hoped to cap his career with the construction of the Locks, ill health forced him to retire in 1909, though he continued lobbying Congress for the project, and served as a consulting engineer and as a Seattle port commissioner until his death in October 1917.

During heavy or prolonged rain, stormwater runoff and overflowing wastewater from neighborhoods along the Ship Canal is dumped into the waterway.

The practice was found to be polluting Salmon Bay and Puget Sound with an average of 130 spills per year dumping 90 million US gallons (340 Ml) of untreated wastewater.

The U.S. Environmental Protection Agency and Washington State Department of Ecology ordered the Seattle city government to address the issue, signing a consent decree in 2016 to plan a diversion system.

[14] The pump station in Ballard is planned to be a 65-foot-tall (20 m) cylinder covered in a steel lattice structure that reaches 80 feet (24 m) in height; it is expected to cost $100 million.

[20] The Lake Washington Ship Canal and the Hiram M. Chittenden Locks are listed on the National Register of Historic Places.