Hoover Dam, ance kent as Boulder Dam, is a concrete arch-gravity dam in the Black Canyon o the Colorado River, on the border atween the U.S. states o Nevada an Arizona. It wis constructit atween 1931 an 1936 during the Great Depression an wis dedicatit on September 30, 1935, bi Preses Franklin D. Roosevelt. Its construction wis the result o a massive effort involvin thoosands o wirkers, an cost ower ane hunder lives. The dam wis controversially named efter Preses Herbert Hoover.