In 2023, the Census Bureau's County Business Patterns series reported that there were 4,192 Electric Power Generation establishments in the United States. These included 561 Hydroelectric, 1,788 Fossil Fuel, 166 Nuclear, 779 Solar, 611 Wind, 48 Geothermal, 116 Biomass, and 123 Other electric power generation establishments. These establishments employed 134,570 people during the pay period that included March 12, 2023.

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In the wake of disastrous floods in the early 1900s, residents of the American Southwest sought the federal government's help to control the Colorado River. Before any work to control the river could begin, Congress had to approve funding and allocate water rights among the seven states in the Colorado River Basin (Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming) needed allocation. Herbert Hoover advocated funding the construction of a dam after becoming Secretary of Commerce in 1921. When the Colorado River Basin states established the Colorado River Commission in 1921, President Warren Harding appointed Hoover as its chair. Hoover negotiated the Colorado River Compact on November 24, 1922, that split the seven basin states into upper and lower halves with jurisdiction to allocate water rights to the individual states.

Between 1922 and 1928, Congress rejected several bills introduced to by Rep. Phil D. Swing (R-CA) and Sen. Hiram W. Johnson (R-CA) to fund construction of a Colorado River dam. In December 1928, Congress passed Swing and Johnson's Boulder Canyon Act (written with Hoover's assistance). Then-President Calvin Coolidge signed the measure into law later that month authorizing $165 million for the project as well as the Imperial Dam and All- American Canal.

The U.S. Bureau of Reclamation released detailed documents for construction companies to review and called for bids to work on the project using government-issued materials. The government received three bids. On March 11, 1931, the federal government awarded the contract to Six Companies, Inc.—a joint venture of construction and engineering companies—which submitted a bid of $48,890,955. Two months later, workers began constructing four 56-foot tunnels to divert the Colorado River around the dam construction site. By November 1932, workers completed the river diversion and had removed more than 1.5 million cubic yards of rock and earth from the riverbed and canyon walls. The first concrete flowed into forms on June 6, 1933, and at the peak of construction, on-site facilities supplied 5,000 cubic yards of concrete every day. On May 29, 1935, workers poured the last of 3.25 million cubic yards of concrete used to build the dam. 

With the bulk of heavy construction completed, President Franklin D. Roosevelt dedicated Boulder Dam during a September 30, 1935, ceremony that was attended by thousands despite the blazing hot temperature. Secretary of the Interior Harold L. Ickes formally accepted delivery of the dam and its power generation plant from Six Companies, Inc., on March 1, 1936. Engineers began filling Lake Mead—named for Elwood Mead, commissioner of the U.S. Bureau of Reclamation—on February 1, 1935. The lake filled sufficiently for the power plant to begin generating electricity and transmitting it to Los Angeles, CA, on October 9, 1936.

The dam project was Initially called the Boulder Canyon Project and Boulder Dam. During a September 17, 1930, groundbreaking ceremony, Secretary of the Interior Ray Lyman Wilbur renamed it Hoover Dam in honor of then-President Herbert Hoover, who had championed and helped secure legislation and funding for the project. Following Hoover's defeat by Franklin D. Roosevelt in the 1932 presidential election, the new Secretary of the Interior Harold L. Ickes and the Roosevelt Administration began calling the structure Boulder Dam. A joint resolution of Congress changed the name back to Hoover Dam and President Harry S. Truman signed the bill into law on April 30, 1947.

Revenue from Hoover Dam electricity repaid the cost of construction, with interest, by 1987. The dam helps supply irrigation to more than 1.5 million acres of land; serves as a water source for 16 million people, including those in major cities like Las Vegas, Los Angeles, and Phoenix; and provides clean energy to over 500,000 homes in the southwestern United States.

You can learn more about important dams, like the Hoover Dam, and power generation using data and records collected by the U.S. Census Bureau. For example:

• The Bureau of Reclamation and Six Companies, Inc. founded Boulder City, Nevada, in 1931 to house approximately 5,000 construction workers hired to build Hoover Dam. The Census Bureau prepared an enumeration district map for Boulder City and counted its population as part of Clark County, Nevada, in 1940. That year, Clark County had a population of 16,414 people. In 1950, Clark County had a population of 48,289 and Boulder City had 3,903 inhabitants. By 2024, Clark County's population had grown to 2,398,871 and Boulder City was home to 15,029 Boulderites.
• The United States Army Corps of Engineers recognizes the Old Oaken Bucket Pond Dam in Scituate, Massachusetts, as the oldest dam in America. Constructed in 1640, the earthen dam was built to create a water reservoir. The dam and reservoir still supply water to residents of Scituate today. The 1850 Census first listed Scituate in Plymouth County when it had 2,149 inhabitants. In 2024, the Census Bureau estimated Scituate was home to 19,598 people.
• Some of the largest and most famous hydroelectric power generating dams in the United States are owned and operated by the U.S. Bureau of Land Reclamation or the U.S. Army Corps of Engineers including the Hoover, Grand Coulee, and Bonneville dams. Many other dams helping to generate hydroelectric power are owned by utility companies. Examples of some of these privately owned hydroelectric dams include the Conowingo Hydroelectric Generating Station in Cecil County, Maryland; Brownlee Dam on the Snake River bordering Washington County, Idaho, and Baker County, Oregon; and the Jocassee Dam on the Keowee River between Pickens and Oconee Counties, South Carolina. The Census Bureau's County Business Patterns series collects data about Hydroelectric Power Generation (NAICS 221111) firms in the United States. In 2023, there were 561 hydroelectric power generation establishments in the United States. These establishments employed 4,156 employees during the pay period that included March 12, 2023.
• President Franklin D. Roosevelt's New Deal dam building projects like the Hoover, Grand Coulee, Bonneville dams and Tennessee Valley Authority controlled river flooding, provided irrigation to farms, improved river navigation, and supplied electricity to regions of the United States that did not have access to affordable power to homes. In 1920, 34.7 percent of all dwellings and just 1.6 percent of farms had electric service. In 1930, 68.2 percent of dwellings and 10.4 percent of farms reported having electricity. By 1940, hydroelectric power accounted for more than 40 percent of the United States' supply of electricity and the number of dwellings reporting electric service rose to 78.7 percent while 32.6 percent of farms had electricity. By 1956, 98.8 percent of dwellings and 95.9 percent of farms had electric service. 
• Utilities like electricity, gas, water, and sewer service are significant monthly costs for American households. Of the nation's 127.4 million occupied housing units in 2023, more than 121.4 million paid for electricity and most households—nearly 28 million—paid $100 to $149 a month for electricity. Approximately 62.6 million paid for gas for heating and cooking. The majority of households with utility-supplied gas service—nearly 14.6 million—paid $25 to $49 monthly. Of the more than 87.3 million households that paid for water and sewer service, nearly 25 million paid more than $1,000 annually.
• The American electric grid is generally so reliable that most people don't think about their home's electricity supply until there is a power outage. However, in October 2024, the Census Bureau reported that 33.9 million households experienced an electrical outage in the 12 months before being interviewed for the 2023 American Housing Survey (AHS). Of those households, 23.9 million reported an outage lasting more than six hours. Of the 15 largest U.S. metropolitan areas, households in Detroit, Michigan, were most likely to report a power outage (44.8 percent) in the previous 12 months, followed by San Francisco, California (36.3 percent); Seattle, Washington (29.3 percent); Houston, Texas (25.7 percent); and Boston, Massachusetts (25.3 percent). As a result of power outages, the AHS data showed that 2.4 million households had at least one member miss work; 4.9 million had food spoil; 2.9 million stayed somewhere else overnight; more than 700,000 households had medicine spoil or had water pipes freeze; and about 300,000 had basement or crawlspace flooding due to the loss of power to a sump pump.
• Electricity does not only light and heat our homes, power our appliances, and recharge our telephones and electric vehicles. American Community Survey data indicate that electricity is also the second most common heating fuel in the United States behind natural gas supplied by a utility. Of the nation's nearly 127.5 households in 2023, more than 59.6 million used utility-supplied gas and 52 million used electricity as the primary source of heating fuel.
• Did you know that Niagara Falls in Niagara Falls, New York, was the site of the first hydroelectric generating facility in the United States? In 1881, Charles Brush—an American electrical engineer, inventor and entrepreneur known for his contributions to the development of commercial electric lighting—opened Schoellkopf Power Station No. 1 by connecting a generator to turbines powered by the falls. The electricity produced powered carbon arc lights for tourists visiting Niagara Falls at night. One year later, the Vulcan Street Plant in Appleton, Wisconsin, became the first commercial hydroelectric power station in the United States. The Appleton Paper and Pulp Company built the hydroelectric power station on the Fox River to supply power to its mill and nearby businesses.
• The North American beaver (Castor canadensis) is famous for being one of nature's greatest dam builders because it builds dams and lodges from tree branches, rocks, mud, and grass. Its fur, meat, and castoreum—an oily secretion used in perfumes and food flavoring—were so valuable, this beaver species was nearly hunted to extinction. Today, these dam-building rodents have inspired the names of a number of U.S. communities, including Beaver, Iowa; Beaver Crossing, Nebraska; Beaver Falls, Pennsylvania; and Beaverton, Oregon.

On September 7, 1989, President George H.W. Bush nominated Barbara Everitt Bryant as the Census Bureau's first female director.

Bryant earned a bachelor's degree in physics from Cornell University. After her three children started school, she attended Michigan State University and received a master's degree in journalism in 1967 and a doctorate in communications three years later. While working at Market Opinion Research headquartered in Detroit, Michigan, she directed national research for three presidential commissions: President Gerald Ford’s Commission on Observance of International Women’s Year (1975-77), President Jimmy Carter’s Commission on World Hunger (1980) and President Ronald Reagan’s Commission on Americans Outdoors (1986). She also managed survey studies and consulting projects for media, transportation, education and health care organizations.

Bryant became Census Bureau director after most of the planning for the 1990 Census had been completed, but led the actual enumeration and the agency's response to accusations of an undercount. She was also proponent of the agency's move toward computer-assisted enumeration.

Bryant left the Census Bureau in 1993. She took a position at the University of Michigan’s Ross School of Business, where she was both a research scientist and director of the American Customer Satisfaction Index. She was active in the American Marketing Association, serving on its board and foundation board, and the American Association of Public Opinion Research. She also was a board member of the Roper Center for Public Opinion Research and a fellow of the American Statistical Association.

On January 19, 1993, Bryant participated in an oral history interview shortly after stepping down as Census Bureau director.