The Hoover Dam, formerly named the Boulder Dam, is located on the Arizona-Nevada state border in Black Canyon, thirty miles southeast of Las Vegas. Constructed between 1930 and 1936 it was the largest dam in the world when it was completed and is still the highest concrete arch dam in the United States. The dam is 726 feet high, 660 feet thick at the base and 45 feet thick at the top. Lake Mead, formed by the dam, is one of the largest man-made lakes in the world at 115 miles long.