Hoover Dam

Formerly called Boulder Dam, the Hoover Dam is located between Nevada and Arizona on the Colorado River. The dam is 1,244 feet (379 meters) long at the crest (top) and 726 feet (221 meters) high, making it the highest concrete arch dam (dam formed by a concrete structure that curves upstream) in the United States. It is 660 feet (201 meters) thick at the base and 45 feet (13.7 meters) thick at the crest (top). It stores 21.25 million acre-feet (26.23 million cubic meters) of water in the 115-mile (185-kilometer) long, artificially created Lake Mead reservoir.

Before the dam was built, the Southwest was faced with constantly recurring cycles of flood and drought. In response, the Boulder Canyon Project Act was enacted on December 21, 1928. The act mandated a dam be constructed on the Colorado River to provide water to the region year-round and to prevent flooding in the low-lying valleys.