The structure was first named Boulder Dam because of existing legislation but was renamed Hoover Dam in 1930 as a tribute to President Herbert Hoover by his Secretary of Interior. Three years later, his successor in the new Franklin D. Roosevelt administration renamed it Boulder Dam. Finally, in 1947, Congress officially reinstated the name Hoover Dam.

The steep-walled Black Canyon was an ideal site for an arch-gravity dam. John Lucian Savage, the Bureau of Reclamation's chief design engineer, created a structure to rise 727 ft above its foundation and have a crest length of 1,282 ft. Construction was awarded to Six Companies Inc., a joint venture of Morrison-Knudsen Co., Utah Construction Co., J. F. Shea Co., Pacific Bridge Co., MacDonald & Kahn Ltd. and an interior joint venture of W. A. Bechtel Co., Henry J. Kaiser, and Warren Bros. Six Companies was formed because no single company could raise $5 million for the performance bond. Its $48.9-million low bid won it the largest single contract ever let by the U.S. government.

Even with six previous large dams under his supervision, Construction Superintendent Francis T. Crowe of MK found a challenge. The site's remote desert location, 30 miles southeast of Las Vegas, first required construction of a town for 5,000 with all utilities and services.

The Colorado, whose flow varied from 2,000 to 200,000 cu ft per second, could be diverted only during winter. The contract called for diversion by Oct. 1, 1933, and a $3,000-per-day penalty for every day beyond that. Crowe aimed to divert the river in the winter of 1932-33. Four diversion tunnels, two on each side, had to be excavated. Each was 4,000 ft long and 56 ft diameter and was lined with 3 ft of concrete. Ingenuity and invention were everyday affairs at the dam, including introduction of the drilling jumbo. It was four platforms welded to a truck and carried 30 rock drills. Crowe drove the tunnels 24 hours a day, seven days a week. Summer temperatures in the tunnels reached 140¡F. Heat prostration killed a worker every other day.

Defying general mining practice, Six Companies used gasoline-fueled trucks in the tunnels, adding carbon monoxide to the heat, dust and blasting fumes. Tunnel work began in May 1931 and was completed by April 1932. These were the second largest tunnels ever mined. The diversion tunnels and upstream and downstream cofferdams were completed more than a year ahead of schedule. At bid preparation, Six Companies gave high prices for work on the diversion phase and lower prices for later work. This produced a high early payoff that allowed it to recover the $5-million initial investment. The success of this maneuver rested on Crowe's ability to place the dam's 3.4 million cu yd of concrete for $2.70 a yard, 35% below the price of the second-low bidder. He not only placed concrete at less than that price but did it ahead of schedule.

Ten aerial cableways crossed the canyon. Five were 20-ton cableways strung from rail-mounted towers to deliver material and workers quickly to any point. The canyon floor was excavated to 125 ft and grouted as deep as 150 ft. "High scalers" hung in bosun's chairs along the cliffs to remove loose rock with jackhammers. The first 8-cu-yd bottom-dump bucket of concrete went into the dam 18 months ahead of schedule. The dam's great mass of concrete was stripped of heat by pumping refrigerated water through 590 miles of pipe placed in the concrete as it was poured. The four 395-ft intake towers were taller than most buildings. The powerhouse's two 230-ft-high wings were designed to house 17 generating units. First power was produced in October 1936, more than two years ahead of schedule.