Hoover Dam was constructed between 1931 and 1936, during the great depression. The dam is a concrete arch-gravity dam and was built to control the flow of the Colorado River, which was necessary to prevent floods and help with irrigation. The dam still holds many engineering records and during its construction was the largest concrete structure to be built, with some of the techniques used never used before. If they tried to build the dam with single continuous pour of concrete it would take more than 125 years to cool. More than 4 million cubic yards of concrete were used for building the dam and later the power plant. Thousands of workers worked on this project with over a hundred losing their lives during construction.
Hoover Dam is fed by Lake Mead, which is the largest water reservoir in the United States by volume. The dam is located on the border of Arizona and Nevada, which creates an interesting situation since the states belong into two different time zones, thus when you cross over half way, you either gain or lose an hour depending on which direction you are walking.
The size of this engineering project can honestly be understood only once you are standing on the top of the dam and looking down at the wall that separates lake mead from the other side. It is a testament to great commitment to a project seemingly impossible to build during the times it was engineered. When you visit Hoover Dam, make sure that you go see the movie about how it was made, it is very educational. Additionally, I would strongly recommend going on the excursion that takes you down into the old intake tunnels. It is an eerie experience, knowing that you are hundreds of feet under water, especially when you see water seeping through the walls, but only through this experience can one truly understand the incredible achievement of actually building this dam.
Enjoy your stay in Las Vegas and make some road-trips to Hoover Dam and national parks nearby.