When Grand Coulee Dam was being built during the depths of the Great Depression, everything about it–generators, powerhouses, pumps–was the biggest in the world. Grand Coulee was more than a dam; it was a proclamation: America could still do great things. The mile-long behemoth was the largest hydroelectric power-producing facility in the world when it was completed in March 1941–just in time to power the nation's defense plants and the atomic reactors for the Manhattan Project. After the war, a vast irrigation project made possible by the dam helped transform the barren deserts of central Washington into rich farmland. But despite its tremendous achievements–including the plentiful production of clean energy–the negative consequences of its construction are equally noteworthy. In a single stroke, Grand Coulee prevented access to one of the greatest salmon rivers in the world, threatening huge populations of fish with extinction, depriving the local Native people of their most important economic and spiritual resource, and instigating a profound cultural decline as waters behind the dam inundated towns, sacred spaces, and burial grounds.