On December 21, 1928, President Coolidge signed the act authorizing construction of a civilian engineering project, the likes of which the world had never seen: a 726-foot-tall concrete structure that would dam the wild and flood-prone Colorado River at a cost of $49 million. By 1931, as the Great Depression continued to erode national confidence, the dam came to symbolize American resilience, its can-do spirit, and know-how. On this, the 75th anniversary of the year of its dedication, Hoover Dam requires no major repairs and is universally acknowledged as one of the great examples of engineering prowess. 

Planning for the dam took a major step forward in 1922 when Herbert Hoover, then Secretary of Commerce under President Harding, negotiated the hard-won Colorado Compact, an agreement between seven western states that traded existing water rights for a fair share of the greater advantage to come. Although Hoover is often maligned for his inadequacy as president during the Great Depression, his deft backroom diplomacy would spur major economic recovery. 

The project brought thousands of unemployed Americans into the desert 28 miles outside of Las Vegas who were seeking the 3000 construction jobs necessary to redirect the course of the Colorado, clear the canyon walls, and pour concrete enough to fill 1333 Olympic swimming pools.

In 1920, the elder statesman William Jennings Bryan envisioned that the proposed dam would transform “barren desert into a garden of wondrous productivity.” His words would prove remarkably prescient. Before the dam was finished, only a handful of hardy people inhabited the vast desert lands of southern Nevada and Arizona. Today, 25 million residents draw their daily water from the 115-mile-long Lake Mead that Hoover Dam created. It’s hard to imagine how Los Angeles, San Diego, Phoenix, Denver, and Salt Lake City would have grown to their present size and prosperity without this water. Over time, the water would help promote the growth of California and the rest of the sunbelt. Hoover Dam’s 17 turbines generate 4 billion kilowatt-hours annually, which power 1.3 million homes. Lake Mead’s waters irrigate an immense and lucrative agro-industry.

Observers of the time recognized that the Hoover Dam, which opened in 1935, marked a turning point. “This is the first glimpse of what chemistry and mathematics and engineering and large-scale organization can accomplish when collective planning unites and inspires them,” said the awed English writer J. B. Preistley. As it neared completion, many of the contractors turned to helping build the Golden Gate Bridge. The dam’s success rapidly encouraged the building of three more great dams. Major tunnels and more bridges soon followed, along with the nation’s earliest freeways—and America exercised its power to create great engineering ventures on an altogether-new scale.