what lake is held back by the hoover dam?
4 Hoover Dam. Hoover Dam is one of the world's great engineering marvels. This massive structure, completed in 1935, crosses the Colorado River, linking Arizona and Nevada. It is 726 feet high and 1,244 feet long. Lake Mead, held back by the Hoover Dam, is the largest artificial lake in the United States. It is 110 miles long, and holds the equivalent of two years of flow of the Colorado River.