John Day Dam, 219 ft (67 m) high and 5,640 ft (1,719 m) long, on the Columbia River between Oregon and Wash.; built between 1959 and 1968 by the U.S. Army Corps of Engineers. It is an extremely large generator of hydroelectric power. The dam's reservoir regulates navigation upstream; locks provide ship passage from The Dalles Dam reservoir to McNary Dam (see Columbia basin project).