Hoover Dam is the highest and third largest concrete dam in the United States. The dam, powerplant, and high-voltage switchyards are located in the Black Canyon of the Colorado River on the Arizona-Nevada state line. Lake Mead, the reservoir behind the dam, will hold the average two-year flow of the Colorado River. Hoover Dam´s authorized purposes are: first, river regulation, improvement of navigation, and flood control; second, delivery of stored water for irrigation and other domestic uses; and third, power generation.   


The project was authorized by the act of December 21, 1928 (45 Stat. 1057), subject to the terms of the Colorado River Compact. The act authorized the construction of a dam and powerplant in either Boulder or Black Canyon, and the All-American Canal System in southern California. The Boulder Canyon Project Adjustment Act (54 Stat. 774), dated July 19, 1940, provided for certain changes in the original plan. On August 17, 1984, Congress passed the Hoover Power Plant Act of 1984. This act authorized an increase in the capacity of the existing generating equipment at the Hoover Dam power plant, and the improvement of parking, visitor facilities, and roadways and other facilities to contribute to the safety and sufficiency of visitor access to Hoover Dam and Powerplant. 


Construction began in Black Canyon in 1931 and the dam was dedicated on September 30, 1935. The first generator of the powerhouse was in full operation on October 26, 1936. The last generator went into operation on December 1, 1961. Construction efforts consisted of re-routing the river through canyon walls, blasting immense amounts of rock and dredging efforts to build on a bedrock foundation, construction of two diversion coffer dams, and pouring 6.6 million tons of concrete. Little changed at the dam until construction of new visitor facilities at Hoover Dam was initiated in 1986. Construction of the visitor building and parking garage was initiated in 1991, and the new facilities – the visitor center, parking structure, and a new penstock viewing platform – were opened to the public on June 21, 1995.  


Irrigation – Ensures dependable water supplies for southern California and southwestern Arizona agriculture. These irrigated lands supply large amounts of produce and other agricultural products for the Nation’s markets.  

Municipal and industrial water supply – Helps shore up scarce municipal and industrial water supplies in the arid southwest. More than 16 million people in the desert southwest receive Colorado River water stored by the project. 

Recreation and wildlife – The engineering marvel of Hoover Dam attracts over 1 million visitors annually to take guided tours. Over 9 million people a year enjoy the recreation afforded by Lake Mead National Recreation Area. Popular activities include camping, picnicking, swimming, boating, water skiing, hunting and year-round fishing.  

Flood control – Prior to construction of the project communities along the lower Colorado River were often devastated by destructive and demoralizing floods. The varying, unpredictable, and rampant flows of the river made it difficult if not impossible to maintain a sustainable and prosperous community along its borders. Hoover Dam has virtually ended the possibility of devastating floods striking the lower reaches of the river as they did prior to project construction.  

Hydroelectric power – Hoover Dam is one of the world’s largest producers of hydroelectric power, generating, on average, four billion kilowatt-hours of energy annually. This energy played a vital role in the production of airplanes and other equipment during World War II, and it also was instrumental in development of industrial expansion in the Southwest. Power generated at Hoover Dam is provided to 15 contractors in the States of California, Arizona and Nevada under contracts that were signed in 1987, and will expire in 2017. The approximate percentage of power delivered to each state is: Nevada – 23.4 % Arizona 19 % California 57.6 %.


  1. Hoover Dam is 726 ft. tall. That is 171 ft. taller than the Washington Monument in Washington D.C. and twice as tall as the Luxor Casino (338 ft.) in Las Vegas, Nevada.
  2. At its base, Hoover Dam is as thick (660 ft.) as two footballs fields measured end-to-end.
  3. As many as 20,000 vehicles a day drive across the 45 ft. wide top of the dam between Nevada and Arizona.
  4. There is enough concrete in Hoover Dam (4 1/2 million cubic yards) to build a 2 lane road from Seattle, Washington to Miami, Florida or a 4 ft. wide sidewalk around the Earth at the Equator.
  5. During peak electricity periods, enough water runs through the generators to fill 15 average sized swimming pools (20,000 gallons each) in 1 second.
  6. Each of the 30 ft. wide penstocks (water pipes) can carry enough water to fill 900 bath tubs (100 gallons each) in 1 second, or 960,000 (12 oz.) cans of drink in 1 second.
  7. Hoover Dam is shaped like a huge curved axe head, 45 ft. wide at the top and 660 ft. thick at the bottom.
  8. Lake Mead is the largest reservoir in the USA and contains enough water to flood the entire state of New York with 1 ft. of water (26 million acre ft.).
  9. If you drink water from the tap at Disneyland, Anaheim or Sea World in San Diego — that water is coming from the Colorado River and Lake Mead, 300 miles away.
  10. Each of the 17 generators can supply electricity to 100,000 households.
  11. When operating at full power, the 17 generators can supply all the electricity needed by a city of 750,000 people.
  12. Each generator weights (4 million pounds) as much as 4 1/2 fully loaded Boeing 747-400’s.
  13. The Colorado River is more than 1,400 miles long and supplies water to Los Angeles, San Diego, and Phoenix. Las Vegas gets almost all its water from Lake Mead. Lake Mead was made by Hoover Dam when it blocked the Colorado River and flooded the Mojave Desert.
  14. Between 1931 and 1936 when the dam was built, 96 men were killed in industrial accidents. None were buried in the concrete.
  15. The mascot dog and favorite pet of all the construction workers during the building of the dam was buried at Hoover Dam. The grave is near the Hoover Dam Tour Center and can be visited.
  16. It would take $2,000,000 worth of copper pennies to make the copper buses (4 inch in diameter hollow square wires) that carry electricity inside the powerhouse.
  17. Every state in the USA furnished supplies and materials for the construction of the dam.
  18. More than 8.5 million pounds of dynamite was used to blast the foundation for the dam and 8 miles of tunnels through the canyon walls.
  19. There are 2,700 miles of transmission lines sending electricity from Hoover Dam to Los Angeles

Last modified on July 18th, 2023