As the United States was growing and expanding in the early 20th century, westward towns needed a stable supply of electricity and water to ensure survival. Given much of the barren landscape in the western U.S., a hydroelectric dam seemed to be the best solution to stabilizing westward expansion.
In 1928, Congress authorized the construction of the Hoover Dam, then known as the Boulder Dam. This structure was to be located in the Black Canyon area in Nevada and Arizona, which is ultimately where the modern dam sits. Construction began in 1931 and was completed in 1936. At the climax of the project, it employed 5,251 workers in an environment that would regularly reach 120 degrees Fahrenheit (49˚C).
The Hoover Dam is the largest concrete framework dam in America and is a massive tourist attraction for people across the globe. It supplies water to farms in the surrounding desert region, water to cities like Los Angeles and Los Vegas, and it generates electricity for nearly 8 million people in the U.S. states of Arizona, California, and Nevada. While certainly not the largest dam in the world, this impressive feat of engineering changed the course of American history.
Here you can see workmen ready to start their shift. Each day they would ride up this platform, called a skip, that ran to the top of the construction site. If you haven't assumed it already, construction of the dam wasn't always the safest. Over the five-year span of construction, 112 people died from work-related accidents. That's an average of nearly 2 people a month.
Construction of this one-of-a-kind project also required some unique tooling. Here you can see large steel formwork that was used to transport the massive concrete arches to the right. These arches would eventually be placed to form the diversion tunnels through the surrounding rocks to allow for emergency flow and energy generation at the Dam.
Building concrete forms deep in layers of rock also wasn't exactly standard operation for construction projects at the time. This railed steel bucket machine would carry loads of concrete deep within the tunnels.
Here you can see just the massive size of the dam's diversion tunnels. Workers here are pouring arch framework in place for the bottoms of the tunnels. 41 of the 112 deaths occurred in these tunnels due to constant breakouts of pneumonia, according to doctors at the time. However, it's largely believed that workers actually died due to carbon monoxide poisoning in the tunnels, and the supervising construction company misrepresented their deaths to avoid paying for death compensation.
As you might be able to guess, the construction of this project required massive amounts of concrete. Here you can see the concrete production plant that held enormous piles of aggregate and sand for the mixing process.
Crews even constructed rail lines around the site simply for the movement of larger equipment. Here, you'll see sections of the dam's main gate ready to be moved and placed. At the time, these rail systems were the most efficient way to move large objects.
Modern concrete pouring uses specialized machines, but in the 1930s, workers had to rely on dump buckets being pulled on-site. The process was arduous, and the work was dark and gloomy. For many of the workers, however, it was the only source of steady income.
These men are from the U.S. Bureau of Reclamation, who oversaw the construction of the Hoover Dam. The construction itself was done by a consortium of companies united under the name Six Companies, Incorporated.
The Hoover Dam restricts the flow of the Colorado River. Here, you can see the upstream flow of the river prior to the beginning of construction on the dam.
Since much of the project consisted of drilling through rock, the engineers and workers devised some of the most innovative drilling procedures of the day. Workers would line this massive platform with their individual drills and slowly make work of the rock ahead of them. This job was loud, dark, and arguably one of the most arduous on-site, but it was crucial to the project.
Here you can see the top of the movable skip that carried workers seen earlier. The dam itself is a work of engineering, but it's incredible to see all the work that went into auxiliary structures for the site.
Pouring the concrete for the main structure of the dam was the biggest undertaking of all of the project – and the most important. If this structure was built improperly, it could fail and kill millions after the dam was put into operation.
Extensive networks of wooden framework were used to shape and create the lining of the dam.
The gate mechanism on the dam wasn't just a tiny door, it was a massive structure. Here you can see some of the large mechanical pieces that went into this mechanism.
With a project that employed so many in an area that was otherwise barren of civilization, the workers on the project were a diverse bunch, from native Apache Indians to migrant workers that traveled from the east coast. Steady well-paying work was highly desired in the 1930s, the middle of the Great Depression, and this project offered that up.
This railed train crane was custom built for the project. Here, you can see it loading a 19-ton piece of cable system track onto the rail car.
While the site had a main concrete mixing plant, there were also several smaller plants spread out around the site that allowed the production of concrete to be fast and effective. You can grasp the scale of this micro-plant by noting the person standing on top of the transit mixer in the bottom right.
The cables used to carry workers to their stations each day were not small. These spools contained the cables used for just that purpose. If one of these cables failed, tens to hundreds of workers would perish, so they had to be up to the task.
The native Apache people employed on the project mostly worked as "high-scalers." These crews would secure equipment and material in otherwise hard to reach places. The natives were attuned to the topography of the site and were the best suited for the job.
Here you can see yet another mixing plant. 2.5 million cubic meters of concrete was used in the project.
This view is from the top of the dam structure near the end of the project. Off in the distance, you can see a remote mixing plant and the railways used to transport equipment.
Finally, on September 30, 1935, U.S. President Franklin D. Roosevelt stopped by the dam for a formal dedication. A year later, in 1936, the hydroelectric plant was finally turned on, and electricity was provided to the surrounding cities and states.
In 1947, the dam was officially named the Hoover Dam and was the largest manmade structure in the world. Its construction created Lake Mead, the largest single reservoir in the United States.
The Hoover Dam may not be the largest dam in the world, but it's definitely near the top of the charts in terms of historical intrigue and interest. There are thousands of photos documenting the construction of the dam in the Library of Congress and the national archive, marking one of the most interesting projects in the 20th century.