- The Lake Washington Ship Canal’s opening was celebrated on July 4, 1917, exactly 63 years after Seattle pioneer Thomas Mercer (1813-1898) first proposed the idea of connecting the saltwater of Puget Sound to the freshwater of Lake Washington via Lake Union. For five decades following Mercer’s suggestion, local citizens, business leaders, government officials, military officers, and entrepreneurs discussed where to build the connection and how to pay for it. Finally, after Hiram M. Chittenden (1858-1917) took charge of the Seattle District of the Army Corps of Engineers in 1906, plans were made and federal funding obtained. The ship canal Chittenden designed consisted of two cuts, the Fremont Cut between Salmon Bay and Lake Union and the Montlake Cut between Lake Union and Lake Washington, and a set of locks at the west end of Salmon Bay. 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.