When it comes to dams, there are plenty to consider. There is China’s Three Gorges Dam that is so big that it slows the earth’s rotation. There is another Chinese dam whose collapse was the greatest structural failure in history. There is the world’s largest dam that happens to have been built by beavers. And, of course, there is the one that Rhett Butler didn’t give Scarlet O’Hara.

Of all of them, however, the best known is nearly 100 years old. When it was built, it was an engineering marvel. It still stands as a towering monument to man’s ability to harness the forces of nature. We refer, of course, to the mighty Hoover Dam.

Built to tame the Colorado River, the Hoover Dam was constructed between 1931 and 1935. In that relatively short span of time, it became the largest man-made structure on the planet. The engineering feat is particularly impressive in that it was built while the world was in the worst days of the Great Depression.

With a height of 726.4 feet (221 meters), the Hoover Dam became the tallest in the world when it was completed. That record has since been surpassed and is now held by the 1,001-foot (305 meters) Liangshan-I Dam in Liangshan, Sichuan, China. Today, it is the second tallest dam in the United States, yielding its record to the 770-foot-high (235 meters) Oroville Dam in Northern California.

Although no longer the largest, the Hoover Dam is still an impressive piece of engineering. Built to be a hydroelectric station, it has an installed capacity of 2,080 megawatts (MW) and currently generates around 4 billion kilowatt-hours (kWh) of hydroelectric power annually. It generates powers for homes and businesses in Nevada, Arizona, and California.

It took 3.25 million cubic yards of concrete for the dam itself and another 1.1 million cubic yards for the power plant and supporting facilities. If spread out, that much concrete could have built over 3,000 miles (5,000 km) of roads, connecting the east and west coasts of the United States. In addition to the concrete, the project required 5 million barrels of cement — nearly the total amount used by the Bureau of Reclamation in all of its previous 27 years of existence.

Ordinarily, that much concrete would have taken 125 years to cool, and it would have made the finished product weak and susceptible to breakage. To overcome this hurdle, engineers created a massive refrigeration machine that generated about 1,000 tons of ice every day. This permitted the unprecedented use of so much concrete in such a confined space in a comparatively short time. Without the creation of the refrigeration process, the timeframe for building the dam would have increased by several decades.

All told, about 21,000 men worked on the dam, an average of 3,500 each day. For their labor, the men were paid an hourly wage ranging between 50 cents and $1.25.

The work was dangerous. Urban legends abound, suggesting that the bodies of unfortunate workers are entombed in the massive structure. That is not true, but the hazardous conditions took a toll. Between cases of accidental falling, unfortunate contact with heavy equipment, and impact from falling rocks, at least 96 men were killed while working on the dam.

The first victim was J.G. Tierney. He was working as a surveyor on December 19, 1922, while the project was in the planning stages. He fell into the river and drowned.

Coincidentally — and freakishly — the last death attributed to the Hoover Dam construction took place 13 years later, to the very day. The last worker to lose his life on the project was Patrick W. Tierney — the son of the dam’s first victim.