Hoover Dam Construction (1931-1936)

About

The Bureau of Reclamation wanted a dam that could tame the lower Colorado River and store a year-round water supply for the Southwest. Congress passed the Boulder Canyon Project Act in 1928, and in 1931 Interior Secretary Ray Lyman Wilbur chose Black Canyon, about 30 miles southeast of Las Vegas. The labour contract went to Six Companies of San Francisco, a group of six major Western builders, for $48,890,995.50, the largest labour contract the federal government had let up to that time.

The work was brutal. Temperatures in the canyon reached 110 to 120 degrees, and higher inside the diversion tunnels. The government rushed Boulder City into existence seven miles from the site to house workers, and crews drove four tunnels to divert the river before excavating the riverbed. The dam was poured as about 215 interlocking blocks, cooled by more than 582 miles of embedded pipe carrying ice water. Concrete placement ran from June 6, 1933, to May 29, 1935, and every feature was finished by March 1, 1936.

A total of 21,000 men worked on the dam, with a daily peak of 5,218 in June 1934. The Bureau of Reclamation counts 96 official "industrial fatalities": men killed at the site by drowning, blasting, falling rock, falls and equipment. Higher figures, such as 112, include deaths before construction began or from causes such as heat and illness. Reclamation is clear that no one is buried in the concrete.

For Las Vegas, the dam changed everything. The town had about 5,200 residents in 1930; the Online Nevada Encyclopedia puts the population at 7,500 by 1931. Dam workers spent their pay in town, especially after Nevada legalized casino gambling that March, and the construction site became a tourist attraction: 100,000 people visited in 1932 and 265,000 in 1934, many stopping in Las Vegas on the way. The dam began generating power in 1937, and Lake Mead's water supply later made the metro area's growth possible.

What to expect

Hoover Dam is open to the public daily from 5 a.m. to 9 p.m., and the Bureau of Reclamation's visitor services run daily from 9 a.m. to 5 p.m. except Thanksgiving and Christmas Day. Options include a Power Plant Tour, a self-guided exhibit tour and a guided Dam Tour through the inspection tunnels. Dam Tour tickets are sold on site only, first come, first served. As of August 19, 2026, Reclamation posted that Dam Tours were unavailable until further notice because of elevator repairs, while the other tours ran normally. Parking on the Nevada side costs $10 per vehicle.

More from the 1930s

• Nevada Legalizes Gambling (1931)

Before and after

• The Founding of Las Vegas (1905)

Good to know

• All vehicles pass through a security checkpoint on the Nevada side, and drivers may be asked to open the trunk, hood and storage areas.
• Interagency Passes such as America the Beautiful are not accepted for the Visitor Center or tours, because Hoover Dam is self-funded.
• The dam was renamed Boulder Dam in 1933 and Congress restored the name Hoover Dam in 1947.
• When finished in 1935 it was the tallest dam in the world, and from about 1938 to 1948 its powerplant was the largest hydroelectric plant in the world, according to Reclamation.
• Drones, firearms, explosives, fireworks and marijuana are all prohibited on Hoover Dam property under federal regulations.
• Visitors under 16 cannot take a tour by themselves, and tours include elevators and tunnels.

Questions about Hoover Dam Construction (1931-1936)