History of the Grand Canyon area stretched along a 278-mile (447 km) segment of the Colorado River from the southern border of Glen Canyon National Recreation Area to the eastern boundary of Lake Mead National Recreation Area. Grand Canyon National Park was designated a World Heritage Site on October 24, 1979. In 1935, Hoover Dam started to impound Lake Mead south of the canyon. Conservationists lost a battle to save upstream Glen Canyon from becoming a reservoir. The Glen Canyon Dam was completed in 1966 to control flooding and to provide water and hydroelectric power. Seasonal variations of high flow and flooding in the spring and
Hells Canyon Dam Hells Canyon Dam Hells Canyon Dam is a concrete gravity dam on the Snake River (river mile 247) in Hells Canyon on the Idaho-Oregon border. The dam impounds the Snake River in Hells Canyon Reservoir; its spillway elevation is above sea level. It is the third and final hydroelectric dam of the Hells Canyon Project, which includes Brownlee Dam (1959) and Oxbow Dam (1961), all built and operated by Idaho Power Company. The Hells Canyon Complex on the Snake River is the largest privately owned hydroelectric power complex in the nation, according to the US Energy Information Administration. The contractor