Hoover Dam

Hoover Dam was authorized by Congress in 1928 and built between 1931 and 1936, two years ahead of schedule. The project employed 21,000 workers at the height of the Great Depression and shaped the city of Las Vegas, which was a small railroad town when construction began. The dam was originally known as Boulder Dam; it was renamed Hoover Dam in 1947 after a vigorous political fight. It remains one of the most iconic public works projects in American history.

Hoover Dam provides electricity to roughly 1.3 million people across Nevada, Arizona, and California, with most of the output going to Southern California (including Los Angeles). The reservoir it created, Lake Mead, is the largest reservoir in the United States by volume and a critical water source for over 25 million people in seven states. The Colorado River Compact—the legal framework that divides the river's water among the upper and lower basin states—was designed around assumptions about Hoover's storage capacity.

Hoover Dam blocks fish migration along the Colorado River and has altered downstream sediment, temperature, and salinity patterns severely enough that several native fish species (notably the razorback sucker and humpback chub) are now endangered. Lake Mead has lost roughly half its volume since 2000 due to drought and over-allocation, dropping to its lowest level since being filled in 2022. Persistent low water levels reduce Hoover's generating capacity—if Mead falls below 950 feet of elevation, the turbines can no longer generate at all.

The Colorado River's allocations were set during an unusually wet decade in the 1920s, and modern hydrologists have long argued that the river is structurally over-promised. The ongoing dispute over how to share dwindling water—the so-called "Lower Basin shortage"—directly affects Hoover's ability to generate electricity.

• 112 workers died during construction, the first in 1922 (a surveyor) and the last in 1935—exactly 13 years to the day later, in the same family.
• The dam contains 4.4 million cubic yards of concrete—enough to pave a two-lane highway from San Francisco to New York.
• When poured, the concrete was cooled by 582 miles of one-inch steel pipe carrying refrigerated water through the structure.
• Hoover Dam is featured prominently in films, TV shows, and video games (Fallout: New Vegas, Transformers, Superman, San Andreas) more than almost any other piece of US infrastructure.