Which dam in Washington State is the largest hydroelectric power station in the U.S.?

Grand Coulee Dam is the largest hydroelectric power station in the United States by installed nameplate capacity. Built across the Columbia River in Washington, its generating facilities have an installed capacity of about 6,809 megawatts.

Construction began in 1933 and the main dam was completed in 1942. The project expanded substantially with the Third Power Plant, completed in the 1970s, and later pump-generating equipment. Together, the facilities contain conventional hydroelectric generators and pump-generators, allowing the complex to produce power while also moving irrigation water.

Grand Coulee was created as the centerpiece of the Columbia Basin Project. Its reservoir, Franklin D. Roosevelt Lake, supplies water for agriculture across central Washington, while the dam's electricity helped power the Pacific Northwest's industrial growth during World War II.

The wording matters: Grand Coulee is the largest U.S. hydroelectric facility by installed capacity, not necessarily the nation's largest power plant by annual electricity generation. That distinction explains why nuclear facilities can rank higher in some yearly-output comparisons. The dam is also different from nearby Chief Joseph Dam and from Hoover Dam, which is famous but considerably smaller in generating capacity.