Hoover Dam, 726 ft (221 m) high and 1,244 ft (379 m) long, on the Colorado River between Nev. and Ariz.; one of the world's largest dams. Built between 1931 and 1936 by the U.S. Bureau of Reclamation, the dam is named for President Herbert Hoover; from 1933 to 1947 it was known as Boulder Dam. A key unit on the Colorado, the dam is a major supplier of hydroelectric power and provides for flood control, river regulation, and improved navigation. Hoover Dam impounds Lake Mead, the largest reservoir in the United States; water is used to irrigate more than 650,000 acres (263,000 hectares) in S California and Arizona, and c.400,000 acres (162,000 hectares) in Mexico. Hoover Dam is part of Lake Mead National Recreation Area (see National Parks and Monuments, table). Boulder City, Nev., was built to house workers on the project.
Hoover Dam, once known as Boulder Dam, is a concrete arch-gravity dam.
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