Lake Mead is the largest reservoir in the United States. It is located on the Colorado River about 30 miles (48 km) southeast of Las Vegas, Nevada, in the states of Nevada and Arizona. Formed by water impounded by the Hoover Dam, it extends 112 miles (180 km) behind the dam, holding approximately 28.5 million-acre feet (35 km³) of water.

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 U.S. states of Arizona and Nevada. When completed in 1936, it was both the world's largest hydroelectric power generating station and the world's largest concrete structure. It was surpassed in both these...