Hoover Dam, Colorado River, United States

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Hoover Dam, once known as Boulder Dam, is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between the US states of Arizona and Nevada. It was constructed between 1931 and 1936, and was dedicated on September 30, 1935, by President Franklin Roosevelt. Its construction was the result of a massive effort involving thousands of workers, and cost over one hundred lives.

Since about 1900, the Black Canyon and nearby Boulder Canyon had been investigated for their potential to support a dam that would control