Washington State Route 17 Coulee City–Brewster branch of PSH 10 was codified in 1931 as a branch of State Road 10 and re-codified in 1937, during the creation of the primary and secondary state highways; however, the highway was not built between Sims Corner and Bridgeport until the 1950s. The Soap Lake–Coulee City branch of PSH 7 was established in 1937 to serve as an alternate route to SSH 2F, avoiding the Grand Coulee Dam. In 1951, the PSH 10 branch between Bridgeport and Brewster was moved north of the Columbia River via the newly built Columbia River Bridge on the present route of
Grand Coulee Dam The dam's powerhouse began production around the time World War II began, and its electricity was vital to the war effort. The dam powered aluminum smelters in Longview and Vancouver, Washington, Boeing factories in Seattle and Vancouver, and Portland's shipyards. In 1943, its electricity was also used for plutonium production in Richland, Washington, at the Hanford Site, which was part of the top-secret Manhattan Project. The demand for power at that project was so great that in 1943, two generators originally intended for the Shasta Dam were installed at Grand Coulee to hurry the generator installation schedule. Water is pumped