Hoover Dam, constructed between 1931 and 1936, was one of the greatest American construction achievements of the 20th century. It was dedicated on September 30, 1935, by President Franklin D. Roosevelt.
On average, the project employed 3,500 workers, peaking at 5,200 workers. More than 100 people died during construction. It was originally known as Boulder Dam from 1933, but was officially renamed Hoover Dam by a joint resolution of Congress in 1947.
The dam is 726 feet tall and 1,244 feet long. It is 660 feet wide at the base and 45 feet wide at the top.
It provides water storage for Lake Mead and generates hydroelectric power through massive power turbines. Four 395-foot tall intake towers, each controlled by two 32-foot diameter cylinder gates, discharge into tunnels that branch into 16, 13-foot diameter power penstocks feeding 17 turbines, nine on the Arizona wing and eight on the Nevada wing. According to the U.S. Bureau of Reclamation, the turbines generate 4 billion kilowatt-hours of hydroelectric power each year for use in Nevada, Arizona, and California - enough to serve 1.3 million people.
This general view of Black Canyon on the Colorado River, looking upstream toward the site of Hoover Dam, shows a temporary steel suspension bridge in the foreground and portals of the 56-inch diversion tunnel bores which will carry the river water while the dam is under construction, March 12, 1932. The dam will be in Black Canyon, despite the fact that it is generally known as the Boulder Canyon Project. (AP Photo)
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This photograph was made from the Nevada side of the river, and shows some of the blasting operations in progress, Aug. 24, 1932 in Nevada. Some idea of the difficulties of the operations may be gained from this view of the rock cliffs. (AP Photo)
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This view shows the interior of one of the tunnels through which the Colorado River will be diverted around the Hoover Dam site in Boulder City, Nev., April 18, 1932. The project is in the early stages of construction. (AP Photo)
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Looking down on Hoover Dam site, the parapet is directly over the power plant site, and also part of the Nevada-Arizona highway which will traverse the dam, shown Aug. 24, 1932. Beyond this will be the greatest lake ever created by man. (AP Photo)
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A lake covering 227 miles will form the 30,500,000 acre foot reservoir from Hoover Dam when completed. Elmer L. Chapman, junior reclamation service engineer, points to the hills which will be submerged after the completion of the project in Nevada, Aug. 24, 1932. The flat top lone mountain in the center of the photograph will be an island 14 feet above water. (AP Photo)
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This is a downstream view of the Hoover Dam showing the immense concrete blocks rising from the bedrock of Black Canyon's floor, which will be the core of the dam, near Boulder City, Nev., Aug. 12, 1933. Concrete is being poured into the forms at the rate of about 6,000 cubic yards daily. (AP Photo)
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Construction continues Jan. 9, 1932 as workers construct the retaining wall that gives support to the road leading over the top of Hoover Dam. Labor troubles were experienced during the huge engineering project on the Colorado River near Las Vegas, Nevada. (AP Photo)
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Gravel screening and washing plant in 1934. Glaha, Ben D., 1899-1970, photographer
Library of Congress
Boulder Dam, (i.e. Hoover Dam) between Arizona and Nevada in 1933. Placing concrete in the sidewall of the Nevada spillway. A 2 cubic yard bottom-dump bucket is being handled by crane. Note the manner in which the panels are staggered
Library of Congress
Penstock on trailer, 1934. Glaha, Ben D., 1899-1970, photographer
Library of Congress
The Nevada intake towers at Boulder Dam in 1934. Glaha, Ben D., 1899-1970, photographer
Library of Congress
Grouting concrete lining in 50' diameter diversion tunnel in 1934. Glaha, Ben D., 1899-1970, photographer
Library of Congress
Construction of the Hoover Dam continues, a constant stream of large trucks dumping fifty tons of soil a minute, built an earth fill dam across the Colorado River, forcing its turbulent waters into two fifty-foot diversion tunnels on the Arizona canyon wall on Nov. 15, 1932. (AP Photo)
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Inside of diversion tunnel no. 3, on the boulder dam project, showing concreting operations, July 9, 1934. The intersection of the inclined tunnel from the intake tower (above) with the present diversion which is being plugged. These tunnels will carry the 30-foot diameter steel penstocks for the power system. Photo by bureau of reclamation. (AP Photo)
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This is an aerial view of one of the four intake towers of the Hoover Dam, Aug. 9, 1934. The towers, two on each side of the canyon upstream from the dam, will measure at 380 feet high. (AP Photo)
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The Boulder Dam, Black Canyon of Colorado River, is nearing completion, this view showing 500 of its projected 730 feet above the canyon floor, Aug. 28, 1934. The federal reclamation service, directing the construction, says the dam, now 80 per center completed will be finished next April, a full year ahead of schedule. (AP Photo)
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A view of the huge Boulder Dam operation from a high point on the Nevada rim of the Black Canyon, shown Sept. 11, 1934. The immensity of the project can be seen from this picture. (AP Photo)
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Hoover Dam takes shape from the concrete columns in which it was poured (shot from cableway control tower downstream on Nevada rim, so looking upstream) in 1934.
U.S. Bureau of Reclamation
The rarely-seen upstream face of Hoover Dam, May 1935
U.S. Bureau of Reclamation
This is a view of the Hoover Dam from upstream as construction continues near Boulder City, Nev., Feb. 1, 1935. The crack in the upper center of the dam is a space left open for cooling and settling of the concrete and will be filled as work progresses. (AP Photo)
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This aerial view shows a crest of the Hoover Dam, aka Boulder Dam, showing the highway leading across it on July 16, 1935. The road, soon to be opened to the public, will provide an easy route between Las Vegas, Nev., and Kingman, Arizona. The intake towers jut up on the other side of the dam in Boulder City, Nevada. (AP Photo)
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Night view of Boulder Dam and Mead Lake taken from a plane United airlines-western air express shows the roadway over the dam top illuminated and the candles atop the intake towers casting their reflections on the water, Sept.22, 1936 in Boulder City, Nevada. (AP Photo)
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Behind boulder dam, in the black canyon of the Colorado River, is the largest man-made lake in the world shown, June 11, 1938. Pressing against the barrier of concrete and steel are 20,000,000 acre-feet of water which, translated into gallons, is enough to provide 51,100 gallons for every person in the United States. This water is to be used to meet the needs of the power house at the toe of the dam, and to irrigate the thousands of acres of reclaimed desert downstream in Arizona and California. (AP Photo)
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Meet the Champs. These six 82,500 kva generators in the Nevada wing of the power house at Boulder Dam are the biggest in the word, Feb.7, 1939 . Power produced at the dam by these generators and one in the Arizona wing, amounts to 130,000,000 kilowatt hours of energy each month which sells for ?290,000. The Bureau of Reclamation which built and operates the dam, received $3,297,289 in two years. Production at this time is approximately one-third of the ultimate capacity. (AP Photo)
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Aerial view of Hoover (Boulder) Dam on the Colorado River, Dec. 11, 1948. (AP Photo)
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This is Main Street in Boulder City, Nevada, Aug. 24, 1932, the model construction housing center for the workers on the huge Hoover Dam project. This city was constructed at a cost of $2,000,000. (AP Photo)
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A three million pound gate of tunnel no. 4, shown above at left, was ready to close, Feb. 1, 1935, stopping flow of the Colorado River at the Boulder Dam, thus starting filling of a huge reservoir. The above photo taken just before the gate stated closing shows a coffer dam built across the entrance of tunnel no. 3, which has been diverting the river through the canyon walls and around the dam on the Arizona side. (AP Photo)
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Spectators watch from bridge over spillway as Boulder Dam overflows for first time, August 6, 1941, and pours 15,000 cubic feet per minute from record level of Lake Mead into Colorado River behind the dam. Spillway leads into tunnel 50 feet in diameter and then 2200 feet to river level below where water bursts out in great jet. At Dam, Lake Mead had reached level of 590 feet and contained more than 10,000,000,000,000 of water. (AP Photo)
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The mighty man-made falls of the Colorado River with the six outlets wide open in a night display. Since the start of generation of power here the dam has been a night-time Mecca for tourists in Los Angeles, Sept. 22, 1936. The transmission of power to Los Angeles will be started on October 9. (AP Photo)
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The 115,000-vollite generator in the world?s biggest power plant, here at Boulder City, Sept. 29, 1936, where all is in readiness to start electricity over the world?s longest power transmission line ? 365 miles to Los Angeles. (AP Photo)
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This magnificent man-made scenic favorite is Hoover Dam by night, May 11, 1953, one of this century?s outstanding triumphs of engineering and construction. At its foot is Lake Mead, the world?s largest man-made body of water on Popular with anglers and fans of boating, Lake Mead is fast becoming a favorite vacation playground. Gateway to the Hoover Dam ? Lake Mead recreational area is fabulous Las Vegas, Nevada on the main line of Union Pacific Railroad. AP Photo)
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The mighty Hoover Dam impresses a young Swiss couple making their first tour of United States on their scooter, April 9, 1954 in Nevada. Natives of Zurich, Fred and Beatrice Troller were veteran scooter travelers in Europe before coming here. (AP Photo)
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Boulder Dam?s mighty water intake towers, rising 395 feet into the air, are in picture of the gigantic power project shown, April 14, 1938. Through these towers flows the water which operates the huge generators in the powerhouse below the 727-foot dam. On the shores of the 110-mile long lake impounded, the government has established the boulder dam recreational area. Luxurious accommodations are available at Boulder City. New a regular airline stop. (AP Photo)
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English: Tourists gather around one of the generators in the Nevada wing of the powerhouse of Boulder Dam (later Hoover Dam) to hear its operation explained.
U.S. Bureau of Reclamation
Hoover Dam at Dusk, Sept. 20, 1950. (AP Photo)
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This July 18, 2014 photo shows generators inside the Hoover Dam, located on the Colorado River, on the border between Arizona and Nevada. It's considered one of America's great civil engineering wonders. Located about a half-hour from Las Vegas, it's a top destination for visitors to the region. (AP Photo/John Marshall)
John Marshall / Associated Press
In this July 28, 2014 photo, lightning strikes over Lake Mead near Hoover Dam at the Lake Mead National Recreation Area in Arizona. On the left are the Arizona intake towers of Hoover Dam. The bathtub ring of light minerals shows the high water mark of the reservoir which has shrunk to its lowest point since it was first filled in the 1930s. (AP Photo/John Locher)
John Locher / Associated Press
Low water levels in the Lake Mead reservoir and at the Hoover Dam show a "bath tub ring" on October 14, 2015. Water in the lake has continued to drop. (Irfan Khan/Los Angeles Times/TNS)
Irfan Khan / Los Angeles Times
A boater gets an up-close view the "bathtub ring" that is visible at low water levels and is the result of the deposition of minerals on previously submerged surfaces while touring the front of Hoover Dam, which sits on the border of Nevada and Arizona, at Lake Mead, Nevada, June 28, 2021.
Allen J. Schaben / Los Angeles Times
The intake towers that feed Hoover Damβs power generators are almost fully exposed as the Lake Mead water level continues to decline in June, 2022.
Luis Sinco / Los Angeles Times