Stretched like a gargantuan wall across the 800ft-deep Black Canyon of the Colorado River, Hoover Dam is a thoroughly practical and intensely dramatic monument to civil engineering, an almost unrivaled example of creativity, efficiency and workmanship. Designed, built and operated by the federal Bureau of Reclamation for flood control and to provide water for irrigation, municipal use, electricity and recreation, it was the world's largest hydroelectric dam from its completion in 1936 until 1949. Rising 726.4ft from a 660ft-thick base to a 45ft-wide crest, capable of producing nearly 50 million kilowatt-hours daily from 17 massive generators, Hoover Dam is the primary catalyst behind the population and economic boom of Arizona and Nevada. The first concrete was poured in June 1933, the last in 1935, two years ahead of schedule. On completion of the power plant, the dam began operation in October 1936. The project (including Boulder City and a nonadjacent canal) was under budget at a cost of $165 million, but 96 construction workers died on the job. From the Visitor Center there are sensational views down the front of the dam and Black Canyon. Video and multimedia presentations focus on the dam's construction; an upstairs gallery is devoted to regional natural history, including a dynamic desert flash-flood demonstration. Visitors may choose between two guided tours of the dam, a shorter sightseeing tour and the more comprehensive Hard-Hat Tour.