Throwback Thursday: Lake Washington Ship Canal is 100 years old

The Lake Washington Ship Canal is nearly 100 years old; its opening celebration was July 4, 1917. But the idea to connect the Puget Sound to Lake Washington was proposed 63 years prior by Thomas Mercer (1813-1898).

According to, it took five decades to decide where to build it and how to pay for it. When Hiram M. Chittenden took over the Seattle District of the Army Corps of Engineers in 1906, the plans were made and federal funding was secured.

Chittenden’s plan included two cuts; the Fremont Cut between Salmon Bay and Lake Union, and the Montlake Cut between Lake Union and Lake Washington. And, of course, the locks, now sharing his name.

“The canal’s construction lowered the water level of Lake Washington by nine feet and raised that of Salmon Bay behind the locks, changing it from a tidal inlet to a freshwater reservoir,” writes David B. Williams for History Link.

With many years of negotiations with community members, Ballard industries and city planners, in 1910, Congress passed a River and Harbor Act that included a $2,275,000 appropriation to build the locks.

The work on the locks started in 1911; the first task of which was to build a cofferdam around the site of the locks. A massive undertaking, “crews dredged 245,000 cubic yards of sediment to create a lock pit, then pumped the water out and began building a 65-foot-high wooden trestle down the center of the pit to support a supply train used throughout the project,” Williams writes.

The concrete was poured in 1913-1914, then the gates were installed a year later, and it was time to connect freshwater to saltwater. On February 2, 1916, it was tested for the first time; the first boat to go through the locks was the Orcas, a tender operated by the Corps.

The grand opening of the locks was on July 4, 1917. According to Williams, the P-I reported that more than half the city’s population lined the shores.

Click here for the full history of the Ship Canal and locks construction from History Link.


Construction of Lake Washington Ship Canal, Seattle, 1912, Photo by A. Curtis, Courtesy UW Special Collections

Hiram M. Chittenden Locks under construction, 1915 Courtesy National Archives

Water gushes from Lake Union into Montlake Cut, Seattle, August 25, 1916 Courtesy MOHAI



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