The Dalles Dam, 260 ft (79 m) high and 8,875 ft (2,705 m) long, on the Columbia River between Oregon and Wash., NE of The Dalles, Oreg.; built 1952-57 by the U.S. Corps of Engineers. The dam, a major link in the development of the Columbia basin, provides hydroelectric power and improves navigation. Located at the head of the slackwater pool created by Bonneville Dam, it impounds a reservoir that provides ship passage 25 mi (40 km) upstream to John Day Dam. Fishways permit salmon and other migratory fish to pass the dam.