Hoover Dam

Congress authorized the Boulder Canyon Project Act in 1928, and construction contracts were awarded in 1931. At the time, it was the largest dam construction project in American history, requiring the excavation of two diversion tunnels totaling 3.5 miles in length to redirect the Colorado River before the main structure could be built.

Six Companies Inc., a consortium of construction firms, employed a peak workforce of approximately 5,251 men in a single day at the height of construction. Workers came from across the United States, many desperate for work during the Depression's worst years. They lived in the government-built Boulder City nearby, a planned community constructed specifically for dam workers.

The Bureau of Reclamation's official count of 96 construction deaths covers falls from structures, drowning in the Colorado, dynamite accidents, and equipment failures. The first recorded death was J.G. Tierney, a surveyor who drowned in the Colorado River on December 20, 1922, during the project's early survey phase. The last recorded death was his son, Patrick Tierney, who died on December 20, 1935 — exactly 13 years later — during the final construction phase. This coincidence was noted in contemporary newspaper coverage and has remained part of the dam's documented history.

Historians and occupational health researchers have argued the official count undercounts the actual toll, particularly deaths attributed to heat stroke and pneumonia from carbon monoxide exposure in the diversion tunnels. The Bureau's criteria for classification as a construction death excluded many fatalities that occurred off-site or were attributed to illness rather than direct accident.

Sculptor Oskar Hansen's bas-relief memorial, dedicated in 1935, stands at the dam's Nevada side. It depicts two winged figures and includes a star map commemorating the dam's completion date. The memorial is a standard stop on Bureau of Reclamation tours.