Hoover Dam from the air
Near the bottom of this aerial photograph, taken on October 30, 1955, is the Hoover Dam, which spans the Colorado River along the Nevada-Arizona border. The concrete arch-gravity dam brought water and power to arid regions of the American southwest and was considered a great engineering feat upon its dedication in 1935. Originally called Boulder Dam, it was renamed in 1947 for President Herbert Hoover, who was involved in its planning and construction while serving as Secretary of Commerce and later as President.
National Archives, Records of the Defense Intelligence Agency