The Hoover Dam is a concrete arch-gravity dam in the Black Canyon of the Colorado River located on the border between Nevada and Arizona. It was constructed between 1931 and 1936 during the Great Depression and it was dedicated on September 30, 1935 by President Franklin D. Roosevelt. Its construction was a massive effort involving thousand of workers and cost over a hundred lives. It was known as Boulder Dam, but renamed Hoover Dam, for President Herbert Hoover, by a joint resolution of Congress in 1947. It cost $49 million dollars in 1931 dollars ($664 million in 2018 dollars).