On September 30, 1935, with a crowd of 10,000 people looking on in 102-degree heat, President Franklin Roosevelt dedicated what was then the world’s biggest dam. Situated on the Nevada-Arizona border, 30 miles southeast of Las Vegas, and stretching 1,244 feet across the Black Canyon, Hoover Dam took five years to construct. Built to control flooding along the Colorado River and provide water and hydroelectric power for California and the Southwest, the dam spurred tremendous growth in that part of the United States. Learn more about this engineering marvel, including why its name once sparked controversy, what happened when it was the target of an alleged German bomb plot and if any bodies are buried in its concrete.

1. The dam’s name was a source of controversy.
Surveyors originally recommended the dam be constructed at Boulder Canyon, leading the initiative to be called the Boulder Canyon Dam Project. Even when Black Canyon later was deemed a better location for the new structure, it continued to be referred to as the Boulder Dam. However, on September 17, 1930, at a ceremony in Nevada to mark the start of construction on a railroad line to the dam site, U.S. Secretary of the Interior Ray Lyman Wilbur announced the dam would be named for his boss, President Herbert Hoover, who had been inaugurated in 1929. In 1933, Hoover was succeeded in the White House by Franklin Roosevelt, and the new secretary of the interior, Harold Ickes, no fan of Hoover, declared the structure would once again be called Boulder Dam. By that point, the name Herbert Hoover also had taken on negative associations for a number of Americans, who blamed him for the Great Depression.

In the ensuing years, Hoover Dam and Boulder Dam were used “interchangeably, the preference often depending on the political leanings of the speaker,” according to Michael Hiltzik, author of “Colossus: Hoover Dam and the Making of the American Century.” Finally, in April 1947, President Harry Truman approved a congressional resolution that officially confirmed the dam would carry Hoover’s name.

2. An entire city was created for people working on the dam.
In the early 1930s, Boulder City, Nevada, was constructed to house 5,000 dam project workers. Before the city was built, many jobless men and their families who’d converged on the dam site, hoping to find employment in the midst of the Great Depression, had lived in squatters’ settlements. Boulder City was situated on federally owned land and had no elected officials. The city was run by an employee of the U.S. Bureau of Reclamation (the agency responsible for the dam project), who had the authority to evict residents as he saw fit. Among the local rules, alcohol and gambling were banned. The Boulder Dam Hotel was erected to host dignitaries coming to see the dam’s construction; famous figures from Bette Davis to the future Pope Pius XII visited in the 1930s. After nearly 30 years, the federal government relinquished control of Boulder City, which was incorporated in 1960.

3. Hoover Dam created America’s largest reservoir.
Formed by the damning of the Colorado River, Lake Mead, the nation’s largest reservoir, covers about 248 square miles and is capable of holding some 28.9 million acre-feet of water (an acre-foot is equivalent to about 325,000 gallons). The creation of Lake Mead (named for Elwood Mead, commissioner of the U.S. Bureau of Reclamation when the dam was being planned and built) flooded the community of St. Thomas, Nevada, and turned it into a ghost town. The last resident of the town, which was settled by Mormon pioneers in 1865, rowed away from his home in 1938. Today, the reservoir supplies water to farms, businesses and millions of people in Nevada, Arizona, California and Mexico. Lake Mead also is a popular site for boating, fishing and swimming; America’s first national recreation area was established there in 1964.

Today, as a result of a drought the Colorado River basin has experienced for the past decade-and-a-half, Lake Mead has dropped to its lowest level since it was first filled in the 1930s.

4. No one was buried alive in the concrete.
Building the dam was too expensive for one company to tackle alone during the Great Depression, so a group of construction firms banded together and, using the name Six Companies, submitted a winning bid of $48.8 million for the project (at the time, it was the largest contract awarded by the federal government). A total of 21,000 men worked on the dam; an average of 3,500 each day, with the daily figure peaking at more than 5,200 in June 1934. When it came to hiring, the contractor was supposed to give preference to veterans of the Spanish-American War and World War I. Six Companies was contractually prohibited from hiring “Mongolian,” or Chinese workers, and while government officials pledged to help ensure that African Americans be employed on the project, the actual amount of black workers hired proved miniscule. A small number of Native Americans were hired as high scalers, responsible for removing loose rock from the canyon walls with jackhammers and dynamite, while suspended from ropes, in preparation for the dam’s construction.

Building the dam was tough, dangerous work, for which men were paid an hourly wage ranging from 50 cents to $1.25. Officially, the project had 96 construction-related fatalities —from such causes as falling rocks and run-ins with heavy equipment—but some sources contend the number likely was higher. Some 4.3 million cubic yards of concrete were used to build the dam, its power plant and auxiliary features, enough concrete to pave a 16-foot-wide, 8-inch-thick road from San Francisco to New York City, according to the Bureau of Reclamation. Contrary to popular myth, no workers were buried alive in the dam’s concrete as it was poured.

5. It once was the Earth’s tallest dam.
Rising 726.4 feet, Hoover Dam was the world’s tallest dam when it was built in the 1930s. These days, it’s the second-tallest dam in the U.S., having been surpassed by the 770-foot-high Oroville Dam in Northern California in 1968. The globe’s tallest dam is the 1,001-foot-high Jinping-I Dam in Liangshan, Sichuan, China, which became operational in 2013.

Hoover Dam’s power plant was the world’s largest hydroelectric station from 1939 to 1949. It has an installed capacity of 2,080 megawatts (MW) and currently generates around 4 billion kilowatt-hours (kWh) of hydroelectric power annually, for homes and business in Nevada, Arizona and California. China’s Three Gorges Dam, which started generating electricity in 2003 and became fully functional nine years later, is considered the planet’s largest hydroelectric dam, with a capacity of 22,500 megawatts. In 2014, Three Gorges broke the global record for annual hydroelectric power production, generating 98.8 billion KWh of electricity. The biggest hydropower producer in the U.S., Washington State’s Grand Coulee Dam, completed in 1941 (a third power station was added in 1974), has a capacity of 6,809 MW and generates about 21 billion kWh of electricity each year.

6. During World War II, the dam was the target of a German bomb plot.
In November 1939, with World War II underway, U.S. officials found out about an alleged plot by German agents to bomb Hoover Dam, by planting bombs at the intake towers to sabotage the power supply to Southern California’s aviation manufacturing industry. After American authorities learned of the plot, private boats were prohibited in the Black Canyon, stricter regulations for dam employees and visitors were enacted and a variety of other security measures such as physical barriers and increased lighting were put in place. Following the attack on Pearl Harbor in December 1941, the dam was closed to visitors for the rest of the war. The dam had its own police force but the Army provided some personnel to help guard the dam. Additionally, government officials investigated various possibilities for protecting the dam from an aerial attack, such as large-scale smoke screens or the construction of a decoy dam, but none of these options were used. Hoover Dam reopened to the general public in September 1945.

7. America’s second-highest bridge now reroutes traffic from the top of the dam.
Since the 1930s, U.S. Route 93 ran right along the top of the dam; however, the two-lane highway was hazardous and had grown increasingly congested over the years. In an effort to remedy these problems, construction began on a dam bypass bridge in 2005. Completed five years later, the Mike O’Callaghan-Pat Tillman Memorial Bridge measures 1,905 feet long and soars nearly 900 feet above the Colorado River, making it the longest single-span concrete arch bridge in the Western Hemisphere as well as the second-highest bridge of any type in America. The structure, which cost $114 million, is named for Donal Neil “Mike” O’Callaghan, a Korean War veteran and two-term Nevada governor during the 1970s, and Pat Tillman, who gave up a professional football career with the Arizona Cardinals to enlist in the Army in 2002; he died in Afghanistan in 2004.