Grand Coulee Dam the Columbia River formed the Grand Coulee, but it was revealed in the mid-late 20th century that massive floods from Lake Missoula carved most of the gorge. The earliest known proposal to irrigate the Grand Coulee with the Columbia River dates to 1892, when the "Coulee City News" and "The Spokesman Review" reported on a scheme by a man named Laughlin McLean to construct a dam across the Columbia River, high enough that water would back up into the Grand Coulee. A dam that size would have its reservoir encroach into Canada, which would violate treaties. Soon after the Bureau
Grand Coulee Dam residents were relocated. The Anti-Speculation Act was passed in 1937, limiting the amount of land farmers could own to prevent inflated prices. The government appraised the land and offered to purchase it from the affected residents. Many refused to accept the offers, and Reclamation filed condemnation suits. Members of the Colville Confederated and Spokane tribes who had settlements within the reservoir zone were also resettled. The Acquisition of Indian Lands for Grand Coulee Dam Act of , 1940, allowed the Secretary of the Interior to acquire land on the Colville and Spokane Reservations, eventually accounting for . By 1942, all