Completed in 1936, the Hoover Dam is America's largest concrete formwork dam and stand as a tourist attraction for people across the globe. Located along the Colorado River in Nevada and Arizona, the tall arch dam took 5 years to complete employing over 5,000 people at peak construction. At the time, Las Vegas was a small city of a little less than 5,000 people, so many workers also came to build housing and infrastructure for the additional population during construction. 112 deaths occurred over the course of construction with causes ranging from drowning to falling. Regardless, the construction was a sight to see and here are some of the most interesting photos out there picturing all of the construction process.

Pictured here are the steel formwork used to transport the concrete diversion tunnel arches [right] into place. There are several diversion tunnels in the rocks around the dam in order to allow for emergency flow and energy generation if needed.

This unique steel bucket machine was used to transport concrete deep within the tunnels.

This is the drilling rig and scaffolding used to tunnel through the thick rock around the dam. While primitive to modern drilling techniques, it was innovative in its day.

Here a greater scope of the diversions tunnels sizes can be seen as workers pour arch formwork in place. There are actually 41 deaths that occurred during construction with the cause being attributed to pneumonia. It is believed that the workers actually died from carbon monoxide poisoning associated with gas vehicles in the tunnel. The cause of death would have been misrepresented by the companies in order to avoid paying for death compensation.

Such a large concrete construction project requires enough material onsite to decrease transportation time. Above you can see the large storage areas of aggregate and the screening of materials.

The concrete application technique of the day simply relied on dump buckets, making the process arduous for workers. Spending one's day in the tunnels would have been a dark and gloomy job, but it was often the only source of income for workers.

The men pictured above are from the U.S. Bureau of Reclamation who oversaw the construction of the Hoover Dam.

This was the view of the Colorado river looking upstream to the site prior to the construction activities of the dam.

One of the most unique pieces of equipment used on the project was the drill rig, then called the "Jumbo Rig." Workers here can be seen with their individual drills on the two level platform moved through the tunnels on rail lines.

This was the movable cable tower used to anchor the skip lines that carried workers to their stations at the beginning of shifts.

With concrete comes formwork, and lots of it. The wooden formwork seen above was used for the diversion tunnel inlet structure which was many stories tall.

The gate mechanism was a key feature of the Hoover dam and it was not a small undertaking. Seen above are the many mechanical pieces of the dam and the hydraulic cylinders can be seen in the background.

The construction site offered up a diverse range of construction workers from the native Apache Indians to migrant workers from afar.

Another piece of custom equipment was the unloading carriage seen here loading a 19 ton permanent cable system onto the rail car.

Several smaller concrete mix plants were used around the site making production of the material fast and effective. You can get a picture of the scale in the image by seeing the person on top of the transit mixer in the bottom right.

With the cableway mentioned previously, comes the need for some large cables and vary long lengths of such. The spools seen above are in storage on site wound with 9 cm diameter steel cable.

The native Apache Indians were employed as "High-scalers" on the project to secure equipment and material in hard to reach places. The men were attune to the topography of the sight and were perfectly matched with the job.

An even bigger expanded concrete mix plant can be seen above as 2.5 million cubic meters of concrete were used in the project.

This is a view offered up from the top of the dam structure with a view of the canyon below and a remote concrete mixing plant on the downstream side of the structure.

The Hoover dam may not be the largest dam in the world, but it holds it's own when it comes to historical intrigue and interest. There are even more photos out there of the dam's construction in what was surely one of the most interesting construction projects of the 20th century.

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