Hoover Dam

Hoover Dam is one of the greatest engineering achievements in American history — a colossal wall of concrete that tamed the Colorado River in the depths of the Great Depression. Rising 726 feet in the rugged Black Canyon on the Arizona–Nevada border, it was the tallest dam in the world when it was finished in 1936, holding back the vast reservoir of Lake Mead. Built ahead of schedule by thousands of workers, it delivers water and hydroelectric power across the Southwest and stands as an enduring symbol of national ambition.

For decades the Colorado River had swung between destructive floods and drought, and by the 1920s the federal government resolved to control it. Congress authorized a great dam in Black Canyon in 1928, and a consortium of contractors called Six Companies, Inc. won the job. Construction began in 1931 amid the Great Depression, drawing thousands of desperate job-seekers to the new town of Boulder City, built to house the workforce.

The work was staggering in scale and danger. Crews first diverted the Colorado through massive tunnels blasted in the canyon walls, then poured more than three million cubic yards of concrete — cooled by miles of embedded pipes to keep it from cracking as it set. The dam rose 726 feet, the tallest in the world at the time. Roughly 21,000 people worked on the project, and official records count 96 construction deaths, with many more from related causes.

The dam was completed in 1936, more than two years ahead of schedule, and President Franklin Roosevelt dedicated it in 1935 as its final sections rose. Its name was long disputed — called Boulder Dam for years before Congress officially settled on Hoover Dam, honoring President Herbert Hoover, in 1947. Behind it spread Lake Mead, the largest reservoir in the United States. Today the dam still supplies water and power across the Southwest and draws millions of visitors.