Grand Coulee Dam: Largest Concrete Structure in the U.S.

The Grand Coulee Dam on the Columbia River in Washington State is the largest concrete structure in the United States by volume. Completed in 1942 after nine years, it stands 550 feet high and 5,220 feet long at its crest, containing over 12 million cubic yards of concrete weighing 18 million tons. Part of the Columbia Basin Project, it provides irrigation, flood control, and over 6,800 MW of hydroelectric power — one of the nation's largest power plants. Its scale epitomizes 20th-century American engineering ambition.