Hoover Dam Timeline

Daring workers called high scalers dangled from ropes hundreds of feet above the canyon floor, drilling and blasting loose rock off the canyon walls so concrete could bond securely to the rock. Their feats became legendary among dam workers.

Massive steel penstocks, some 30 feet in diameter, were fabricated and installed to carry water from intake towers to the turbines in the power plant at the base of the dam, a feat of heavy fabrication for its time.

Engineers embedded more than 582 miles of steel pipe through which chilled water circulated, cooling the concrete. Without this system, the dam would have taken over a century to cool naturally, making it one of the era's great engineering innovations.

Architect Gordon Kaufmann applied Art Deco styling to the dam, its towers, and terraces, while sculptor Oskar Hansen created the Winged Figures of the Republic monument, blending artistry with monumental engineering.

Four towering concrete intake structures were completed on the upstream face of the dam, each fitted with massive cylindrical gatehouses that control the flow of water into the penstocks feeding the power plant.

Rising floodwaters forced operators to use the dam's spillways for the first time. The tests revealed cavitation damage in the spillway tunnels, leading to engineering studies and repairs that improved understanding of high-velocity water flow.

With the diversion tunnels closed, water began backing up behind the dam, forming Lake Mead, the largest reservoir in the United States by volume when full, stretching over 100 miles up the Colorado River.

Image source: Lake Mead

Sculptor Oskar J.W. Hansen's twin bronze winged figures were dedicated at the Nevada abutment, standing as a memorial to the workers who built the dam and symbolizing the nation's optimism and strength.

The last bucket of concrete was placed, topping out the dam two years ahead of schedule. In total, about 4.36 million cubic yards of concrete had been used, enough to pave a road across the continental United States.

Although Secretary of the Interior Ray Lyman Wilbur had named it Hoover Dam in 1930, political controversy led officials to call it Boulder Dam for several years. Congress permanently restored the name Hoover Dam in 1947.

President Roosevelt delivered a dedication speech before a crowd of thousands, hailing the dam as a triumph of engineering and a symbol of hope during the Great Depression. The event marked the formal completion of the project.

The first generator went online, delivering hydroelectric power to Southern California and later Arizona and Nevada. At its completion, Hoover Dam was the largest hydroelectric facility in the world.

After years of the dam being referred to as Boulder Dam, President Harry Truman signed a resolution officially designating the structure as Hoover Dam, honoring the president who authorized the project as commerce secretary.

The dam was designated a National Historic Civil Engineering Landmark and listed on the National Register of Historic Places, recognizing its significance as a masterpiece of engineering and a defining achievement of the New Deal era.

A modern visitor center opened, offering exhibits, observation decks, and guided tours. Today the dam attracts nearly one million visitors annually, remaining one of the most popular tourist destinations in the American Southwest.

A prolonged drought in the Colorado River basin caused Lake Mead's water levels to fall dramatically, exposing long-submerged features and prompting concerns about hydropower capacity and water supplies for millions of people.

The Hoover Dam Bypass Bridge opened, carrying U.S. Route 93 traffic across Black Canyon just downstream of the dam. It relieved the dam's roadway of through traffic and became the first concrete-steel composite arch bridge built in the United States.

Image source: Mike O'Callaghan–Pat Tillman Memorial Bridge

More than eight decades after completion, Hoover Dam continues to produce roughly 4 billion kilowatt-hours of electricity per year, serving about 1.3 million people and standing as an enduring icon of American engineering.