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
Marble Canyon Dam upper dam was located just above the cavern, and was sometimes referred to as Redwall Dam. Marble Canyon Dam The Marble Canyon Dam, also known as the Redwall Dam, was a proposed dam on the Colorado River in Arizona. The dam was intended to impound a relatively small reservoir in the central portion of Marble Canyon to develop hydroelectric power. Plans centered on two sites between miles 30 and 40 in the canyon. At one point a tunnel was proposed to a site just outside Grand Canyon National Park to develop the site's full power generation potential, reducing the Colorado