1931-1936
Building the Hoover Dam
Officials ride in one of the penstock pipes of the soon-to-be-completed Hoover Dam.
In the early years of the 20th century, the rapid development of the southwestern United States was creating a high demand for electricity and water. Simultaneously, a series of catastrophic floods made it clear that the Colorado River needed to be dammed and controlled.
In 1922, the U.S. Reclamation Service settled on Black Canyon as the ideal location for a dam. They had initially chosen Boulder Canyon (unfortunately located on a seismic fault line), which gave the project its first name, Boulder Dam.
Congress authorized the project in 1928; construction began in 1931, under the direction of a consortium called Six Companies, Incorporated.
The Great Depression was in full swing, and tens of thousands of hopeful workers flocked to the dam site with their families, camping out in temperatures that reached 120 degrees Fahrenheit. At its peak, the project employed 5,251 people.
An inspection party near the proposed site of the dam in the Black Canyon on the Colorado River.
A surveyor signals to colleagues during the construction of the dam.
Four tons of dynamite are detonated in the canyon in the early stages of construction.
The first step: diverting the river away from the construction site. Three miles of diversion tunnels were dug on both sides of the river, and huge berms or “cofferdams" were built above and below the site.
With the riverbed dry, excavation began. Millions of tons of loose sediment and rocks were scraped away to reveal bedrock. The design called for an arch-gravity dam, which would transfer the crushing force of the water reservoir to the abutting canyon walls.
To make sure those walls were solid, workers known as “high scalers” had to rappel down them, hammering away anything loose. Falling rocks were a serious hazard, so the workers dipped their hats in tar and let them dry and harden — the first hard hats.
1933
1933
c. 1935
"High scalers" use jackhammers to shave loose rock off the walls of Black Canyon.
"High scalers" rappel down the canyon wall.
In June 1933, the pouring of the concrete began. The chemical reactions which occur during the hardening of concrete generate high levels of heat. Engineers estimated that if the entire dam had been poured as a single concrete block, it would have taken 125 years to cool (and it would have collapsed).
To circumvent this problem, the concrete was poured into discrete rectangular plots called “lifts.” It was then cooled with pipes filled with ice-cold water. By the time the pouring ceased in May 1935, approximately 3.25 million cubic yards of concrete had been used — enough to pave a highway from New York to San Francisco.
Though the myth that there are bodies entombed in the dam is just that, a myth, there were officially 112 deaths as a result of the project. The first was J. G. Tierney, a surveyor who drowned while searching for a spot for the dam on December 20, 1922. The last worker to die on the dam lost his life 13 years to the day later — Tierney’s son, Patrick.
The concrete foundation of the dam is poured into separate blocks called "lifts."
A bucket holding 18 tons of concrete is maneuvered into position.
Concrete is dropped into place.
The base of one of the intake towers under construction.
Student engineers stand atop one of the 2 million-pound hydroelectric generators for the dam at the General Electric factory in Schenectady, New York.
Construction on the dam proceeded day and night.
Workers apply a coat of paint to one of the dam's spillways.
The dam nears completion.
On Sept. 30, 1935, President Franklin D. Roosevelt stopped by the dam for a formal dedication ceremony. A year later, the hydroelectric power plant was finally turned on, providing electricity to cities in California, Nevada and Arizona.
Eventually renamed Hoover Dam in 1947, the dam was the largest manmade structure in the world when completed, and created Lake Mead, the largest reservoir in the United States.
President Franklin D. Roosevelt tours the dam.
