The Hoover Dam, also known as Boulder Dam, is a 726-foot-tall concrete dam that spans the Colorado River at the Arizona-Nevada state border. 1244 feet wide and 660 feet thick at its base, the mammoth Hoover Dam was originally begun in 1931 and completed in 1935, two years ahead of schedule. (Production had been sped up considerably to provide additional jobs during the economic downturn of America’s Great Depression.) The dam is named for Herbert Hoover, who played an instrumental role in its construction, both as Secretary of Commerce and then President of the United States. Today Hoover Dam generates a maximum of 2074 megawatts of hydroelectric power on a daily basis, thanks to the entire flow of the powerful Colorado River passing through its seventeen turbine generators.

Prior to 1931, no project of Hoover Dam’s enormity had ever been undertaken, and many of the procedures used were completely untried. For instance, one significant issue was how to pour the tremendous amount of concrete needed for construction. Engineers determined that since concrete heats up and then contracts, and uneven cooling would pose serious problems to the dam, pouring the dam in a single pass would take 125 years to cool safely. So instead they built the dam with a series of interlocking trapezoidal columns, with each concrete pour no more then six inches deep (making the folk tales about dam workers said to have been buried alive during construction highly improbable). However, 112 deaths did occur during the dam’s construction, most due to carbon monoxide poisoning generated by machinery.

Surprisingly, the architecture of Hoover Dam originally proposed was much different than the iconic structure we see today. The initial design was criticized as being too plain for a project of such scale, and Los Angeles-based architect Gordon B. Kaufmann was hired to redesign the project. Today the dam amazes visitors with its elegant Art Deco exteriors, sculptured turrets and clock faces that tell both Nevada and Arizona (or Pacific and Mountain zone time, respectively). Hoover Dam receives visitors from 8 to 10 million people each year.