Hoover Dam - Facts & Summary - HISTORY.com Google At the turn of the 20th century, farmers sought to divert the Colorado River to budding Southwestern communities via a series of canals. When the Colorado broke through the canals in 1905, creating the inland Salton Sea, the job of controlling the raging river fell to the U.S. Bureau of Reclamation. Bureau director Arthur Powell Davis in 1922 outlined a plan before Congress for a multipurpose dam in Black Canyon, located on the Arizona- Nevada border. Named the Boulder Canyon project, after the original proposed site, the dam would not only control flooding and irrigation, it would generate and sell hydroelectric power to recoup its costs. Still, the proposed $165 price tag concerned some lawmakers, while representatives of six of the seven states in the river drainage area—Colorado, Wyoming , Utah , New Mexico , Arizona and Nevada —worried that the water would primarily go to California . Secretary of Commerce Herbert Hoover brokered the 1922 Colorado River Compact to divide the water proportionally among the seven states, but the legal wrangling continued until outgoing President Calvin Coolidge authorized the Boulder Canyon Project in December 1928.

In honor of the new president’s contributions, Secretary of the Interior Ray L. Wilbur announced the structure would be called Hoover Dam at a 1930 dedication ceremony, though the name didn’t become official until 1947. As the Great Depression unfolded, hopeful laborers descended on Las Vegas and set up camp in the surrounding desert for the chance to work on the project. Those who were hired eventually moved to Boulder City, a community specifically built six miles from the work site to house its employees. Meanwhile, the U.S. government set about finding a contractor to build the proposed 60-story arch dam. The contract was awarded in March 1931 to Six Companies, a group of construction firms that had pooled its resources to meet the steep $5 million performance bond. The first difficult step of construction involved blasting the canyon walls to create four diversion tunnels for the water. Facing strict time deadlines, workers toiled in 140-degree tunnels choked with carbon monoxide and dust, conditions that prompted a six-day strike in August 1931.

When two of the tunnels were complete, the excavated rock was used to form a temporary coffer dam that successfully rechanneled the river’s path in November 1932. The second step of involved the clearing of the walls that would contain the dam. Suspended from heights of up to 800 feet above the canyon floor, high scalers wielded 44-pound jackhammers and metal poles to knock loose material, a treacherous task that resulted in casualties from falling workers, equipment and rocks. Meanwhile, the dried riverbed allowed for construction to begin on the powerplant, four intake towers and the dam itself. Cement was mixed onsite and hoisted across the canyon on one of five 20-ton cableways, a fresh bucket capable of reaching the crews below every 78 seconds. Offsetting the heat generated by cooling concrete, nearly 600 miles of pipe loops were embedded to circulate water through the poured blocks, with workers continually spraying the concrete to keep it moist. As the dam rose, block by block, from the canyon floor, the visual renderings of architect Gordon Kaufmann took form.

Electing to emphasize the imposing mass of the structure, Kaufmann kept the smooth, curved face free of adornment. The powerplant was given a futuristic touch with horizontal aluminum fins for windows, while its interior was designed to pay homage to Native American cultures. With the body of water that would become Lake Mead already beginning to swell behind the dam, the final block of concrete was poured and topped off at 726 feet above the canyon floor in 1935. On September 30, a crowd of 20,000 people watched President Franklin Roosevelt commemorate the magnificent structure’s completion. Approximately 5 million barrels of cement and 45 million pounds of reinforcement steel had gone into what was then the tallest dam in the world, its 6.6 million tons of concrete enough to pave a road from San Francisco to New York City. Altogether, some 21,000 workers contributed to its construction. Hoover Dam fulfilled the goal of disseminating the one-wild Colorado River through the parched Southwest landscape, fueling the development of such major cities as Los Angeles, Las Vegas and Phoenix.

Capable of irrigating 2 million acres, its 17 turbines generate enough electricity to power 1.3 million homes. The dam was designated a National Historic Landmark in 1985 and one of America’s Seven Modern Civil Engineering Wonders in 1994. It receives some 7 million visitors annually, while Lake Mead, the world’s largest reservoir, hosts another 10 million as a popular recreation area. Tags Hoover Dam and the Colorado River Compact, United States | Building the World Hoover Dam and the Colorado River Compact, United States Hoover Dam and the Colorado River Compact, United States Hoover Dam, from Library of Congress at loc.gov. WHY UNITED STATES? The Colorado River, creating hydroelectricity for the bright lights, big city of Las Vegas, Nevada, is also the source of water for seven U.S. states, as well as Mexico, and the Navajo. Although the Hoover Dam was one of the largest river-development projects in the world, it was not the first. Consideration must be given to the ancient Marib Dam.

Dating from around 1050BC, the dam was maintained for centuries in what was called Saba in Arabic or Sheba in the west, whose queen is legendary. Marib Dam was built in a corner of the Arabian Peninsula now known as Yemen. Hoover Dam maintains two distinctions: it is the first example in history of a comprehensive interstate compact to deal with allocation of water rights, and the massive project remains a model of success, completed under budget and two years early. As water and electricity become increasingly valuable, can Hoover Dam inspire a new generation? MACRO The Hoover Dam is actually a system of more than 20 dams along a 2,330 kilometer (1,450 miles) river, affecting an area 632,000 square kilometers (242,000 square miles), with so much concrete as to build a wide sidewalk around the earth at the equator. During peak periods of electrical demand, enough water runs through the generators to fill 15 average-size swimming pools in one second. All of this culminates in the iconic shape of Kauffmann’s arch. Was it any wonder that artist Oskar J.W.

Hansen likened the Hoover Dam to the Pyramids? Additionally, the mighty Colorado River had to be diverted and made dry before work on the dam could begin. Diversion tunnels were blasted through the walls of the canyon by competing teams – one of the many successful organizational ideas of the builders. Blasting and piping teams formed into a kind of intramural tournament; workers were so motivated to win the contest that the tunnels were completed early. MURL EMERY Ragtown, from University of Virginia at virginia.edu. Even before the dam’s construction began, families flocked to the thirty-mile stretch between Las Vegas and the worksite. There were few other employment opportunities while people waited, but Murl Emery came to the rescue. The merchant opened up a general store in a worker camp informally called “Ragtown.” Even when the project started up, Emery allowed families to pay what they could and take what they needed; the balance would be put on account. Emery trusted the workers, and they returned his trust: no one ever failed to pay up. Emery’s remarkable business carried on commerce without government subsidy or contractor support. MACRO SUCCESS MODEL: SIX COMPANIES, INC. A multi-partner effort was needed.

Partners included: Morrison-Knudsen Co. MacDonald & Kahn Ltd. Joint venture of W.A.Bechtel Co., Henry J. Kaiser, and the Warren Brothers Forming a consortium with the practical name of Six Companies, Inc., the partners moved as one. Executive team provisions such as incentives written directly in the contract with bonuses for completion were balanced by fines for running beyond construction deadlines. Work units took incentive provisions very seriously, working both day and night. Innovations abounded including project segments that rivaled Henry Ford’s assembly line. Another reason for success? Legions of recently unemployed laborers who had lost their jobs during the Great Depression. Small armies of workers, whole families along, moved to a certain nearby town called Las Vegas. In many cases, they were free to live on-site, a key to success in large-scale projects. INNOVATION A jumbo, from the US Department of the Interior at usbr.gov. The Jumbo: Workers and management were highly motivated to make or beat project deadlines, thereby winning bonuses. This quest for success gave rise to innovation.

For example, the jumbo truck — a vehicle fitted with layers of platforms on which 20-30 workers stood bracing themselves as the truck rumbled along the canyon.The truck would ride right to the face of a canyon cliff; the sounds that ensued were deafening — everyone would drill at once, making holes that were then stuffed with blasting powder. Entire sections could, in this way, be demolished in one blast. A ton of dynamite was planted every 14 feet. Multiply that method by eight, for that was the number of jumbo trucks working simultaneously. Electric lights were added to the rigs so drilling could rock the canyon around the clock. High Scaler monument, from the US Department of the Interior at usbr.gov. Aerialists: The fabled high-scalers who performed acrobatic feats from aloft were legendary. Local knowledge is powerful; Native Americans familiar with the intricacies of the canyons became fabled high-scalers. These daredevils could have trained for modern day Circe de Soleil. The high-scalers dangled precariously from ropes, scraping off loose rocks remaining after blasting. Well-paid and highly respected, the daredevils’ lofty antics were immortalized by photographers.

Cool: Construction of the dam required 3.25 million cubic yards of concrete; even more was needed for the power plant. Workers built several concrete plants that ran so constantly that a bucket of concrete went out on the overhead cable delivery system every 78 seconds. But there was one problem; it was calculated that it would take 100 years for the concrete to cool. A brilliant innovation resulted: a system for cooling concrete by pouring it in rows and columns that were cooled by 582 miles of steel pipes pumped with ice water. Afterwards, the pipes themselves were emptied of water and filled with concrete, thus strengthening the structure. COMPACT STRUCTURE WITH LOOSE ENDS Upper and lower basins, from the U.S. Bureau of Reclamation, at usbr.gov. If management of the construction was an unparalleled success, government legislation left a few loose ends that soon entangled. The Colorado River Compact, legislation that preceded the building of the dam, authorized seven states to work together to decide how to apportion shared water.

At first, determination was linked to irrigable land within each state, but later the decision to draw a “line” between the Upper and Lower Basins and group the states into two camps seemed the sensible thing to do. Upper Basin states consisted of Wyoming, Colorado, Utah and New Mexico; Lower Basin contained California, Arizona and New Mexico. Upper Basin states would be required to deliver 75 maf (million acre feet, a water-measurement term) each 10 years, a period long enough to even out the natural variances caused by flood or drought. Calculations by the Reclamation Bureau showed that flows could range from 4.4 maf to 22 maf, with 16.4 maf the norm. But problems were downstream. Currently the eighth-largest economy in the world, California was the elephant in the room during 1920 negotiations by the seven states along the basin of the Colorado River. It was apparent to all seven parties that as California grew, that state’s development might impact the other partners. The agreement signed in 1922 was challenged two decades later; the legal case of Arizona v.

California lasted 11 years and cost $5 million, one of the most contentious and expensive litigation cases of the time. The Colorado River Compact left out two parties, Native Americans and Mexico, omissions that would come to haunt. Regarding Native Americans, Herbert Hoover made certain they were at least mentioned: Article VII stipulates, “Nothing in this compact shall be construed as affecting the obligations of the United States to Indian Tribes.” It is possible this phrase refers to the 1903 Supreme Court decision in Winters v. United States, which stated that Native American tribes had water rights whether they were using the water or not, and that their rights were related to the placement of their reservations. Sixty years later, in 1963, the Supreme Court intervened to define the rights of five Native American reservations in the Lower Basin. Of particular note are the Navajo, whose 25,000-square-mile reservation is entirely within the territory of the compact. At a 1997 Colorado River Symposium, an attorney for the Navajo observed that tribe’s water rights approach the five-maf level.

Nothing prevents the Navajo from selling their water; while American states may be subject to federal law, Native American tribes remain sovereign entities protected by the Winters law. FIRST DIVERSITY MANDATED PROJECT IN AMERICAN HISTORY For the first time in public construction history, the federal government mandated a policy of diversity, requiring that African Americans be hired to work on the project. This little-recognized fact makes the Hoover Dam one of the most important achievements in United States’ history. ICONIC Hoover Dam is also significant because it represents a time when government, business, and community alike believed in shared power and shared resources. Energy and water would be created and distributed to the betterment of all. Communicating such a vision required art. After the dam was designed from an engineering perspective, Gordon B. Kauffmann reworked the vision to further elevate it to working art. Kauffmann proposed a system of plain surfaces alternating with shadows. In addition, Oskar J.W. Hansen was commissioned to create two large cast panels of concrete showing the aspects of flood control, irrigation, power, and a history of the area. It was Hansen who included a star map, set in the floor of the dam, which compares the Hoover Dam to the Pyramids.

Document of Authorization ACT ACT TO PROVIDE FOR THE CONSTRUCTION OF WORKS FOR THE PROTECTION AND DEVELOPMENT OF THE COLORADO RIVER BASIN, FOR THE APPROVAL OF THE COLORADO RIVER COMPACT, AND FOR OTHER PURPOSES. Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled. That for the purpose of controlling the floods, improving navigation and regulating the flow of the Colorado River, proving for storage and for the delivery of the stored waters thereof for reclamation of public lands and other beneficial uses exclusively within the United States, and for the generation of electrical energy as a means of making the project herein authorized a self-supporting and financially solvent undertaking… Approved, December 21, 1928. – From Congressional Record, 70th Cong., 2nd sess. (1928), chap. 42, pp. 1057-66. See Building the World, p. 450. COLORADO RIVER COMPACT November 24, 1922 Nothing in this compact shall be construed as affecting the obligations of the United States of America to Indian tribes. Article VII. Approved: Herbert Hoover.

– See Building the World, pp 439. VOICES OF THE FUTURE: Discussion and Implications Native Americans and the Future: Native Americans control some of the water of the Colorado River, and have rights to sell it. The Navajo have 5 maf annually; this may be compared to 1.5 for all of Mexico. Recently, tribes used their special status to build casinos. As water becomes scarce, will the Walapai, Havasupai, and Navajo become leaders in water markets? World Water Academy: With Lake Mead (created by the Hoover Dam), and Lake Chad in Africa, shrinking, is it time to found a college for water study? An early example might be the first of the Grandes Ecoles in France, formed in 1753 under Louis XV, the Ecole des Ponts et Chaussées. This “School of Roads and Bridges” still exists. But there are gaps in the world’s education system, and water planning and management might be one. Should China found a World Water Academy as that country works towards completion date of the Grand Canal in 2050? Or might the University of Massachusetts Boston, located on the Atlantic as what Provost Winston E.

Langley terms a “liquid bridge,” lead the way? RESOURCES To read the complete chapter, members of the University of Massachusetts Boston may access the e-book through Healey Library Catalog and ABC-CLIO here. Alternatively the volumes can be accessed at WorldCat , or at Amazon for purchase. Further resources are available onsite at the University of Massachusetts Boston, Healey Library , including some of following: Building the World Finding Aid (* indicates printed in Notebook series) Bergman, Charles. Red Delta: Fighting for Life at the End of the Colorado River. Golden, CO: Fulcrum Publishing, 2002. Cathcart, Robert. Planet Earth Renewed: Macroprojects and Geopolitics. Monograph. Fifth revision, 1984. Ward, Evan Ray. Border Oasis: Water and the Political Ecology of the Colorado River Delta, 1940-1975. Tucson: University of Arizona Press, 2003. Wilson Richard Guy. “American Modernism in the West: Hoover Dam.” In Images of an American Land, edited by Thomas Carter. Albuquerque: University of New Mexico Press, 1997.

Internet For the Hoover Dam’s official website, see: http// For more on the Hoover Dam as a curved gravity structure: Water and Power Associates Water and Power Associates (1930)* - Black Canyon - The future site of Hoover Dam. Background Hoover Dam was constructed between 1931 and 1936 during the Great Depression. Its main purpose was to harness the Colorado River to prevent periodic catastrophic flooding, to allocate and distribute water, and to generate hydroelectricity for the Southwest. Even by today's standards Hoover Dam was a gigantic project. At the time it was the world's largest project made with concrete, not to mention the largest public works project in US history. The dam's completion had a significant impact on Southern California and in particular Los Angeles, since the power generated by the dam contributed to more than 70% of the City's power needs at the time. (1925)^* - "The Party" about to embark for a trip through Boulder Canyon. They are assessing the potential sites for a dam on the Colorado River. Historical Notes Members of a water resources consulting committee (F. E. Bonner, A. J. Cleary, G. A. Elliot, B. A.

Etcheverry, F. C. Herrmann, Louis C. Hill, W. L. Huber, A. Kempkey, J. B. Lippincott, William Mulholland, and C.S. Ridley) prepare to embark on a trip down the Colorado river, through Boulder Canyon, with representatives of the City of Los Angeles (William Mullholland, H. A. Van Norman, E. A. Bayley, H. C. Gardett, and S. Parratt) and the State of California (Paul Bailey and Gerald Jones).^* More than 200 engineers worked to design the dam that would be constructed in Black Canyon. It would be the highest concrete arch dam in the United States, and the largest building project that the federal government had ever undertaken.*# Historical Notes Before a dam could be built, political work was necessary to resolve the competing claims on the river by different western states. As U.S. secretary of commerce, Herbert Hoover negotiated the Colorado River Compact, which divided the river basin into two regions, lower (Arizona, Nevada and California) and upper (Wyoming, Utah, New Mexico and Colorado) that would make the building of the dam possible.

In 1928, after years of lobbying to get a dam-building bill through Congress, the legislation was finally approved as the Boulder Canyon Project Act. Hoover, who that same year was elected as the 31st president of the United States, signed the bill into law in 1929.*# Historical Notes 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. 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. #* (ca. 1931)^^ - Workmen supported by lines from the top as they did high scaling on canyon walls during construction of the dam. Historical Notes “High Scalers” climbed down canyon walls on ropes to remove loose and weakened rocks along the canyon walls where the dam walls would join. Descending down the cliffs with the weight of tools, water and food, others would lower jackhammers to drill powder holes.

The High Scalers would fill the holes with dynamite and after hand maneuvering out of the way of explosives, they went to work with crowbars to remove loosened rock.*^* (1932)* - View from above the Colorado River looking upstream towards the site of Hoover Dam which is at the bend in the river. On the right we can see the lower portals of the Arizona water diversion tunnels. Historical Notes Before construction could begin, the river was diverted around the dam site through four 50-foot-diameter tunnels, two drilled through the canyon walls on each side of the river. The tunnels, with a total combined length of 15,946 feet, or about three miles, were excavated to 56 feet and lined with three feet (300,000 cubic yards) of concrete. They could carry over 200,000 cubic feet - more than 1.5 million gallons - of water per second. The river was first diverted through the two Arizona tunnels on November 14, 1932.*#^ Historical Notes The Jumbo Rig was designed to speed up the Hoover Dam's tunnel drilling process.

Built on the back of a 10-ton truck, 24 to 30 drills could be operated at once.^ These jumbos had two platforms for drillers to stand on, the third level of men working from the ground. It also had horizontal bars at the three levels, where the pneumatic drills hung by swivels. The process then became: Back the truck up to the solid rock wall, drill the holes, pack them with dynamite, tie them together and then pull the entire truck a safe distance away while the blowman detonated. Then clear away the debris and do it again.*#* (1932)**^ – View showing the interior of one of the tunnels through which the Colorado River will be diverted around the Hoover Dam site., April 18, 1932. (ca. 1933)^#^ - Government officials and politicians take a ride in one of the 30 ft. diameter pipe sections. Historical Notes Forty-four thousand tons of steel were formed and welded into 14,800 feet of pipe varying from 8 1/2 to 30 feet in diameter.

Each length of the largest pipe - 12 feet long, 30 feet in diameter, and 2 3/4 inches thick - was made from 3 steel plates, of such weight that only two plates could be shipped from the steel mill to the fabricating plant on one railroad car. Two such lengths of pipe welded together make one section weighing approximately 135 tons or, at intersections with the penstocks, as much as 186 tons.^*^ Workmen stand in completed spillway tunnel lining at Boulder Dam.* The spillway tunnel is 50 feet in diameter and 2,200 feet in length. Click HERE to view a detail diagram showing Boulder Dam's piping and penstock configuration. Historical Notes Each of the 4 diversion tunnels was holed out to 56-foot diameter—as high as a 4-story building—and lined with a 3-foot thickness of concrete. The total length of the tunnels was approximately 3 miles.**# (1934)* - Five workmen peer at the inside one of the four diversion tunnels. Behind them on the right is another tunnel. Historical Notes The four tunnels would have another important use besides diversion of the river.

After completion of the dam, they would serve to house the outlet works used in the regulation of the reservoir. The two outer tunnels would become outlets for the huge spillways. The two inner tunnels would guide the stored water from the intake towers in the reservoir to the power plant or past it to the outlet valves below the dam.**# (ca. 1933)^^ - Construction was a 24/7 operation. In this view we can see the base of the dam face on the far side of a pool of water, construction equipment and night lights. Historical Notes The first concrete was poured into the dam on June 6, 1933, 18 months ahead of schedule.^ (ca. 1933)* - Hoover Dam initial construction phase. Note the width and depth of the dam as it goes up. Historical Notes Since concrete heats and contracts as it cures, the potential for uneven cooling and contraction of the concrete posed a serious problem. Bureau of Reclamation engineers calculated that if the dam was built in a single continuous pour, the concrete would take 125 years to cool and the resulting stresses would cause the dam to crack and crumble.

Instead, the ground where the dam was to rise was marked with rectangles, and concrete blocks in columns were poured, some as large as 50 feet square and 5 feet high.^ Every state in the USA furnished supplies and materials for the construction of the dam. #* (ca. 1934)* - A closer look at the cement forms for the two power plants. Construction workers can be seen throughout. Historical Notes There were 112 deaths associated with the construction of the dam. Included in that total was J. G. Tierney, a surveyor who drowned on December 20, 1922, while looking for an ideal spot for the dam. He is generally counted as the first man to die in the construction of Hoover Dam. His son, Patrick W. Tierney, was the last man to die working on the dam's construction, 13 years to the day later. Ninety-six of the deaths occurred during construction at the site of the 112 fatalities^.... None were buried in the concrete. #* (1934)#* - View of three men standing by a Packard observing the near completed process of concrete pouring at the dam.

(1935)* - View of the Hoover Dam power plants near completion. The concrete pouring process appears to be complete. Historical Notes A total of 3,250,000 cubic yards of concrete was used in the dam before concrete pouring ceased on May 29, 1935. In addition, 1,110,000 cubic yards were used in the power plant and other works. More than 582 miles of cooling pipes were placed within the concrete. Overall, there is enough concrete in the dam to pave a two-lane highway from San Francisco to New York.^ (ca. 1935)* - View of the giant turbine runner before its installation at Hoover Dam power plant. The fin-like pieces of metal between the two circular flanges are the vanes. (September 30, 1935)* - Dedication of Hoover Dam by President F. D. Roosevelt. Ezra Scattergood can be seen in the lower right behind the chair with the hat. Historical Notes On September 30, 1935, less than 5 years after construction started, President Franklin D.

Roosevelt said in dedication ceremonies at Hoover Dam: “This is an engineering victory of the first order – another great achievement of American resourcefulness, skill and determination. This is why I congratulate you who have created Boulder Dam and on behalf of the Nation say to you, ‘well done’.” ^## In 1920, Ezra Scattergood pushed for a bill authorizing the construction of the Boulder Canyon Project (Hoover Dam). Despite attempts to discredit the project, Scattergood helped convince Congress in 1928 to pass the legislation and allow construction of the dam and a hydroelectric power plant.^# (1936)**^ – A crowd is assembled in the power house of the Hoover Dam in Boulder City, Nev., during ceremonies in which U.S. President Franklin Roosevelt pressed a button in Washington, D.C., starting the 3,500 horsepower generator in the foreground, creating the first power from the dam in Boulder City, September 11, 1936. Historical Notes The City of Los Angeles would have to wait another 28 days (October 9th, 1936) before it would get its allotment of power from Hoover Dam.

(1930s)**^ – View showing the high-voltage switching yard at Boulder Dam, with the steel etched against a black desert sky. Power from the generators at the top of Boulder Dam left this station on the main line to Los Angeles at 287,500 volts. Historical Notes Sixteen high-voltage transmission lines connect Hoover Dam with its power market area. Two lines terminate at Los Angeles, a line a distance of 266 miles. A third line extends to Los Angeles via the McCullough Switching Station, where the energy is stepped up to 500,000 volts. One line extends to San Bernardino, California. Three lines extend to Las Vegas, Nevada. One of the latter connects with the Davis Dam transmission system. Other lines extend to Kingman, Arizona; Needles, California and nearby Boulder City.^^# In total, there are 2700 miles of transmission line cable sending electricity from Hoover Dam to Los Angeles. #* Click HERE to see more in Early Power Transmission.

(October 9, 1936) - Plaque reads: "On the above date Miss Elisabeth Scattergood pressed this key which lighted the electric arc in the Civic Center as the citizens of Los Angeles received their first electric power from the Hoover Dam Hydro Electric Plants of the Colorado River". Construction of Hoover Dam Video Click HERE to view video. Construction of Hoover Dam - Historical Timeline The following timeline takes us from the late 1890’s when the first attempt to control flooding from the Colorado River began to 1936 when the Hoover Dam was completed and electric power flowed to the City of Los Angeles: 1890’s – Initial attempt at diverting the Colorado River for irrigation purposes by the construction of the Alamo Canal by land speculator William Beatty. 1900 – Preliminary investigation and studies for building a dam at Black Canyon or Boulder Canyon with the purpose of controlling floods, providing irrigation water, and producing hydroelectric power. Repeated flooding of the Imperial Valley and other areas created the need to control the Colorado River through construction of a dam.

1902 – Edison Electric Company surveys the Colorado River with the idea of building a 40-foot rock dam which could generate 10,000 horsepower. At this time, however, the limit for transmission of electric power is only 88 miles and there are few customers within that limit. During that same year Edison allows its land options on the river to lapse, including an option for what became the site of Hoover Dam. 1902 - U.S. Congress passes the Reclamation Act to provide for a plan for the payment of construction costs for a reclamation project to control the Colorado River. 1905 – Heavy rainfall and snowmelt causes the Colorado River to swell and overrun a set of Alamo Canal head-gates. This results in a flood which diverts the entire volume of the Colorado River into the Salton Sink over a period of approximately two years before it can be controlled again. This catastrophic event also floods the entire Imperial Valley. The flood completely submerges the town of Salton, Southern Pacific Railroad siding, and Torres-Martinez Indian land.

The Salton Sea is created as a result of the diverted uncontrolled flow of the Colorado River over 50 miles into what was once an ancient dry lakebed in the desert for over two years without drainage. 1906-1907 – Southern Pacific Railroad spends $3 million to stabilize the waterway. 1922 – Reclamation Service (later the Bureau of Reclamation) presents a report calling for building a dam on the Colorado for flood control and power generation. The report concludes that this should become a federal project since the river’s basin covers several states and the river enters Mexico. 1922- Reclamation Service selects Black Canyon as the ideal spot for the dam not the original location of Boulder Canyon since that site is bisected by a fault-line. The name of the project remains ‘Boulder Canyon Project’ despite the site change (See above photo). 1922 – The Colorado River Compact is signed by seven states of the Colorado basin (California, Nevada, Arizona, Utah, new Mexico, Colorado and Wyoming. More than anything this serves to balance each of the affected state’s water rights. 1926 - William Mulholland gets involved with the Boulder Canyon Project even when funding wasn't clearly available.

He makes a commitment to Congress to buy even more power than needed by Los Angeles. The extra power would be used to pump water in a newly planned aqueduct that would bring Colorado River water to Southern California (Colorado Aqueduct, completed 1941). Los Angeles guarantees its power purchases against the federal government's costs for the dam. 1928 – Congress authorizes the project and President Coolidge signs the bill. $165 million is appropriated for the Hoover Dam, the Imperial Dam and the All-American Canal, both downstream. Legislation to authorize construction of the dam has taken years since representatives from other parts of the country found it to be too costly and beneficial to mostly California. Not until the 1927 Mississippi flood did Midwestern and Southern congressmen and senators become more sympathetic to the dam project. 1929 – Six of the seven states approve the compact which is the minimum required to proceed with the project. Arizona does not approve until 1944. 1931 – Start of Construction by a consortium of companies called Six Companies, Inc.

1933 - Ezra Scattergood obtains a $22,799,000 loan from the federal government to build a power transmission line from Hoover Dam to Los Angeles. Construction of the Boulder-LA transmission line begins as the dam itself is erected. 1934 - Congress authorizes a fifty-year contract that defines the how the Hoover Dam's electricity is to be allocated and sold, which would run from 1937 - 1987. The authorization also defines who is to operate the powerhouses within that time frame--both the Los Angeles Department of Water and Power and Southern California Edison. In 1984 the allocation of power would be revised (see 'Current Milestones' below). Also, in 1987 the Bureau of Reclamation assumes control of the powerhouses. 1935 (September 30) – Hoover Dam is dedicated by President Franklin Roosevelt. 1936 (March 1st) – The dam is turned over to the federal government from Six Companies, more than two years ahead of schedule. 1936 (October 9th) – Hoover Dam begins transmitting electricity to Los Angeles.

The DWP built transmission line spans 266 miles of mountains and desert and delivers over 70% of Los Angeles’ power (Hoover Dam delivers less than 6% of LA's power today). The transmission lines included pioneering technology in high-voltage transmission. They transmitted electricity at a higher voltage (287 kV) than any other long-distance transmission line in the world to date. The Naming Controversy: Boulder Dam or Hoover Dam? During the years of lobbying leading up to the passage of legislation authorizing the dam in 1928, the press generally referred to the dam as "Boulder Dam" or as "Boulder Canyon Dam", even though the proposed site had shifted to Black Canyon. The Boulder Canyon Project Act of 1928 (BCPA) never mentions a proposed name or title for the dam. The BCPA merely allows the government to "construct, operate, and maintain a dam and incidental works in the main stream of the Colorado River at Black Canyon or Boulder Canyon".

When Secretary Wilbur spoke at the ceremony starting the building of the railway between Las Vegas and the dam site on September 17, 1930, he named the dam "Hoover Dam", citing a tradition of naming dams after Presidents, though none had been so honored during their terms of office. Wilbur justified his choice on the ground that Hoover was "the great engineer whose vision and persistence ... has done so much to make [the dam] possible". One writer complained in response that "the Great Engineer had quickly drained, ditched, and dammed the country". After Hoover's election defeat in 1932 and the accession of the Roosevelt administration, Secretary Ickes ordered on May 13, 1933 that the dam be referred to as "Boulder Dam". Ickes stated that Wilbur had been imprudent in naming the structure after a sitting president, that Congress had never ratified his choice, and that it had long been referred to as Boulder Dam. When Ickes spoke at the dedication ceremony on September 30, 1935, he was determined, as he recorded in his diary, "to try to nail down for good and all the name Boulder Dam".

At one point in the speech, he spoke the words "Boulder Dam" five times within thirty seconds. Further, he suggested that if the dam were to be named after any one person, it should be for California Senator Hiram Johnson, a lead sponsor of the authorizing legislation. Roosevelt also referred to the dam as Boulder Dam, and the Republican-leaning Los Angeles Times, which at the time of Ickes' name change had run an editorial cartoon showing Ickes ineffectively chipping away at an enormous sign "HOOVER DAM", reran it showing Roosevelt reinforcing Ickes, but having no greater success. In the following years, the name "Boulder Dam" failed to fully take hold, with many Americans using the two names interchangeably and mapmakers divided as to what name should be printed. Memories of the Great Depression faded, and Hoover to some extent rehabilitated himself through good works during and after World War II. In 1947, a bill passed both Houses of Congress unanimously restoring the name to "Hoover Dam".

Ickes, who was by then a private citizen, opposed the change, stating, "I didn't know Hoover was that small a man to take credit for something he had nothing to do with."^ More Recent Milestones 1984 - Congress passes a new statute which sets power allocations from the dam for the period 1987 to 2017. 1987 - The Bureau of Reclamation assumes control of running the powerhouses. Both DWP and SCE operated the powerhouses between 1936 and 1987. 2011 - President Obama signs legislation extending the power allocation contracts until 2067, after setting aside 5% of Hoover Dam's power for sale to Native American tribes, electric cooperatives, and other entities. The new arrangement is to take place in 2017.^ Boulder Dam-LA Transmission Line Click HERE for the Boulder Dam-LA Transmission Line Engineering Paper by E. F. Scattergood, presented to the American Institute of Electrical Engineers in 1935. Hoover Dam Construction | ONE Hoover Dam Construction Image courtesy of the U.S. Bureau of Reclamation.

Hoover Dam, often called Boulder Dam, is located on the Colorado River at the southern tip of Nevada and the Arizona border. In the early 1900s, after many failed efforts to control the lower Colorado River with levees and irrigation canals, the U.S. Bureau of Reclamation decided the best solution for the arid Southwest would be to dam the river and create a year-round water supply. Surveyors investigated seventy sites along the entire river's course and settled on Nevada's Boulder and Black Canyons, both offering a potential reservoir of more than thirty million acre-feet. Surveys revealed the superiority of Black Canyon for storing the Colorado River's entire flow for up to two years, though in 1922 the “Fall-Davis Report” recommended to the U.S. Senate construction of the All-American Canal in California's Imperial Valley and a high dam at or near Boulder Canyon. All seven Colorado River states—Wyoming, Colorado, Utah, New Mexico, Arizona, Nevada, and California—could see the advantages of a dam in the river's lower basin (below Lee's Ferry near the Utah/Arizona boundary), but were concerned for their own interests.

Mining engineer Herbert Hoover, later to be United States President, was a strong proponent of the project and served as presiding officer of the Colorado River Commission, which painstakingly worked out the details of states' water rights, apportioning water to two groups: the upper and lower basin states, which would divide the water rights between themselves at a later date. With that settled, in 1928, Congress passed and President Calvin Coolidge signed the Swing-Johnson bill, better known as the Boulder Canyon Project Act. In 1931, Secretary of the Interior Ray Lyman Wilbur announced that a 726.4-foot high dam would be built in Black Canyon rather than Boulder Canyon due to a fault at the upper end of Boulder Canyon and greater storage capacity in Las Vegas Wash. It would be named Hoover Dam. (But when Hoover lost the presidency to Franklin D. Roosevelt in 1932 because people blamed him for the Great Depression, the dam was officially renamed Boulder Dam in 1933.

Congress restored the name Hoover Dam in 1947.) A labor contract was awarded to Six Companies of San Francisco composed of Utah Construction of Ogden, Utah; Pacific Bridge of Portland, Oregon; Henry J. Kaiser & W.A. Bechtel of Oakland, California; MacDonald & Kahn of Los Angeles; Morrison-Knudsen of Boise, Idaho; and J.F. Shea of Portland, Oregon—all major Western contracting firms. The bid was $48,890,995.50, the largest labor contract let by the U.S. Government up to that time. During the Great Depression, many workers and their families arrived long before work on the dam began in hopes of finding jobs. They lived in jerry-rigged dwellings in makeshift tent camps next to the river. Because the area was totally desolate, with recordings of 110 to 120 degrees in the canyon (later peaking at 140 in the airless portals of the diversion tunnels), much preparation was necessary, including rushing Boulder City, seven miles southwest of the dam site, to completion in fifteen months to provide suitable living conditions for workers.

Railroad lines were built, as were highways, a construction camp, a gravel-screening plant, concrete-mixing plants, air compressor plants, a plate steel fabricating plant, and much more. The plan of attack was to drill four diversion tunnels through the canyon walls during the low-water season of 1932-33, divert the river through the tunnels, build earthen cofferdams above and below the dam site to block the river, de-water and excavate the site, and build the dam and power plant. The two outer tunnels would be outlets for huge spillways; the inner tunnels would convey water from intake towers in the reservoir to the power plant. Many ingenious techniques and devices were developed on this project, such as using dishpan reflectors to light the diversion tunnels, the hard-hat (cloth hats dipped into tar and hardened into a tough shell), the motor-driven jumbo drill equipped with thirty 144-pound rock drills boring into the rock face at the same time to speed up drilling and blasting, and the on-site fabrication of steel pipe for the penstock system because standard railroad cars could not carry the pipe, which exceeded 44,000 tons in gross weight, from eastern fabricating mills.

Six Companies built an aggregate producing and batch plant to supply 4.5 million yards of concrete and gravel. Workers poured concrete into a honeycomb of tiered blocks that ice-cold water running through embedded pipes cooled, solving the problem of intense heat generated by the chemical reactions solidifying concrete. The crest height of the dam was reached in March 1935, two years ahead of schedule, with 3,250,335 cubic yards or 6.6 million tons of concrete poured into the dam structure. Contrary to oft-repeated legend, no one is buried in the concrete, though ninety-six men were officially listed as having died on the project. In twenty-one months, 5,000 men had built a structure greater in volume than the largest pyramid in Egypt, which, according to Herodotus, required 100,000 men working twenty years to build. The American Society of Civil Engineers has named Hoover Dam one of the seven modern civil engineering wonders of the United States. It is listed as a National Historic Landmark. Geographic Area: Timeline . Hoover Dam . American Experience .

WGBH | PBS John Wesley Powell May - August, 1869: Early History Major John Wesley Powell makes the first recorded trip through the Grand Canyon and down the length of the Colorado River. The one-armed Civil War veteran followed this expedition with a second trip down the Colorado in 1871, when he conducted geological studies that greatly expanded understanding of the topography of the region. Library of Congress Theodore Roosevelt June 17, 1902 President Theodore Roosevelt signs the Reclamation Act. Reclamation Service engineers begin their long series of investigations and reports on control and possible uses of the Colorado River. Union Pacific Railroad Workers use train tracks to cross the flooded plain. March, 1905 Torrential rains begin and lead to the Colorado River breaking into the Imperial Valley, creating an inland sea across a hundred and fifty square miles. It was two years, at a cost of more than $3 million, before the river is contained within its original channel. Blaine Hamann, former Bureau of Reclamation employee, recalls, “The river was an enemy, and only in short periods of time could you look at it as a useful river.

Most of the time it was something that would kill you or ruin your farm.” May 18, 1920 Congress passes the Kinkaid Act authorizing the Secretary of the Interior to investigate problems of Imperial Valley. Arthur P. Davis February, 1922 Arthur P. Davis is the chief author of the Fall-Davis report entitled “Problems of Imperial Valley and Vicinity.” Prepared under the Kinkaid Act and submitted to Congress, the report recommended construction of a high dam on the Colorado River at or near Boulder Canyon. The report also suggested that the government could recoup the cost of construction by selling the electric power generated by the dam to the cities in rapidly expanding Southern California. November 24, 1922 Representatives of the seven Colorado River Basin States sign the Colorado River Compact in Santa Fe, New Mexico. Later in the year, the first of the Swing-Johnson bills to authorize a high dam and canal is introduced in Congress. Library of Congress Calvin Coolidge December 21, 1928 The Colorado River Board of California reports favorably on a feasibility study concerning the Boulder Canyon Dam Project.

The Boulder Canyon Project Act, introduced by Senator Hiram Johnson and Representative Phil Swing, both of California, passes in the House and Senate, and is signed by President Calvin Coolidge . Herbert Hoover Presidential Library Herbert Hoover June, 1929 Herbert Hoover takes charge of negotiations as six of seven basin states approve the Colorado River Compact. The basin states include Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming. Arizona, unhappy with the proposed plan for water distribution, is the one state that held out against the Compact. The resulting agreement leads to passage of the Boulder Canyon Project Act. Bureau of Reclamation The men of Six Companies March 11, 1931 The Bureau of Reclamation opens bids for the construction of Boulder (Hoover) Dam and Power Plant. The contract is awarded to Six Companies , a construction and engineering firm made up of some of the West’s most successful builders and designers of dams, bridges, roads, and tunnels. The winning bid was $48,890,995. November 14, 1932 The Colorado River is diverted around the dam site. June 6, 1933 First concrete is poured at Hoover Dam site.

February 1, 1935 The Hoover Dam starts impounding water in Lake Mead. May 29, 1935 The last concrete is poured at the dam site. September 30, 1935 President Franklin D. Roosevelt attends and speaks at the dedication of Boulder (Hoover) Dam. The Hoover Dam completed March 4, 1947 Officially declaring that the dam at Boulder Canyon be named Hoover Dam for former President Herbert Hoover, House Resolution 140 is introduced to Congress. It will pass two days later and move on to be approved in the Senate. April 30, 1947 President Harry S. Truman signs resolution officially declaring that the dam at Boulder Canyon be named Hoover Dam. Hoover Dam | Bureau of Reclamation The Story of Hoover Dam - Articles Chronology Alarcon discovers the Colorado River and explores its lower reaches. Cardenas discovers the Grand Canyon. 1776 Father Escalante explores the upper Colorado and its tributaries. 1857 Lt. J. C. Ives navigates the Colorado River and, with his steamboat The Explorer, reaches the end of Black Canyon.

1869 Major John Wesley Powell makes the first recorded trip through the Grand Canyon. 1902 President Theodore Roosevelt signs the Reclamation Act. Reclamation engineers begin their long series of investigations and reports on control and use of the Colorado 1905-1907 The Colorado River breaks into the Imperial Valley, causing extensive damage and creating the Salton Sea. 1916 Unprecedented flood pours down the Gila River into the Colorado, and flood waters sweep into Yuma Valley. 1918 Arthur P. Davis, Reclamation Director and Chief Engineer, proposes control of the Colorado by a Dam of unprecedented height in Boulder Canyon on the Arizona-Nevada border. 1919 All-American Canal Board recommends construction of the All-American Canal, and a bill is introduced to authorize its construction. 1920 Congress passes Kinkaid Act authorizing Secretary of the Interior to investigate problems of the Imperial Valley. 1922 Fall-Davis report entitled "Problems of Imperial Valley and Vicinity", prepared under the Kinkaid Act and submitted to Congress February 28th, recommends construction of the All-American Canal and a high dam on the Colorado River at or near Boulder Canyon.

Representatives of the seven Colorado River Basin States sign the Colorado River Compact in Santa Fe, New Mexico, November 24th. First of the Swing-Johnson bills to authorize a high dam and canal is introduced in Congress. 1924 Weymouth report expands Fall-Davis report and further recommends Boulder Canyon project construction 1928 Colorado River Board of California reports favorably on feasibility of project. Boulder Canyon Project Act, introduced by Senator Johnson and Representative Swing, passes the Senate December 14th, the House December 18th, and is signed by President Calvin Coolidge, December 21st. 1929 Six of the seven Basin States approve Colorado River Compact. Boulder Canyon Project Act declared effective June 25th. 1930 Contracts for the sale of electrical energy to cover dam and power plant financing are completed. 1931 Bureau of Reclamation opens bids for the construction of Hoover Dam and Power Plant March 4, awards contract to Six Companies, March 11th, and gives contractor notice to proceed April 20th. 1932 River is diverted around the dam site, November 14th.

Repayment contract for the construction of the All-American Canal is completed with Imperial Irrigation District. 1933 First concrete is placed June 6th. 1934 All-American Canal construction begins in August. Repayment contract between the United States and the Coachella Valley Water District covering cost of Coachella Main Canal executed October 15th. 1935 Dam starts impounding water in Lake Mead February 1st. Last concrete is placed in dam May 29th. President Franklin D. Roosevelt dedicates dam September 30th. 1936 First generator, N-2, goes into full operation October 26th. Second generator, N-4, goes into operations November 14th. Third generator, N-1, starts production December 28th. 1937 This Day in History: Construction Began on Hoover Dam | whitehouse.gov This Day in History: Construction Began on Hoover Dam July 7, 2015 at 2:05 PM ET by Molly Wolfe Twitter Facebook Email Summary: On July 7, 1930, construction began on Hoover Dam, a significant accomplishment for infrastructure and sustainable energy in America.

On July 7, 1930, construction began on the Hoover Dam. President Herbert Hoover was deeply devoted to protecting the environment, particularly focusing on pollution-free water, flood control, and fisheries. After a disastrous Mississippi River flood in 1927, Hoover recommitted to bettering American infrastructure to prevent another catastrophe. Before the Dam could be built the Colorado River had to be diverted through tunnels. This piece of equipment, named a Jumbo Rig, was designed to speed up the tunnel drilling process. Built on the back of a 10-ton truck, 24 to 30 drills could be operated at once. (Department of Interior Bureau of Reclamation) “[Hoover] Dam will probably be the biggest dam, perhaps the biggest man-made thing in the whole wide world.” — Fortune Magazine, September 1933 Early construction in Black Canyon (Department of Interior Bureau of Reclamation) Think of it as a giant Lego set, with over 200 blocks fitted together to stand 726 feet tall.

The Hoover Dam has been called the Eighth Wonder of the World, comparable to the Great Pyramids of Egypt, and “a vision in the desert.” In the 1940s, the Hoover Powerplant was the largest hydroelectric installation in the world. Today, over 1.3 million people benefit from the 4 billion kilowatt-hours of hydroelectric power the Dam generates each year. View from dam's crest during test of Jet Flow gates. (Department of Interior Bureau of Reclamation) In addition to being an engineering masterpiece, controlling flooding and generating hydroelectric power, the Dam is a national gem, showcasing diverse artistry. Norwegian immigrant Oskar J.W. Hansen sculpted the Winged Figures of the Republic, a pair of 30-foot bronzed statues which guard the Nevada side of the Dam. Hansen stated that the sentinels symbolize "the immutable calm of intellectual resolution, and the enormous power of trained physical strength, equally enthroned in placid triumph of scientific accomplishment." The angels stand on a magnificent terrazzo floor patterned with a star chart from the 1935 date of dedication by President Franklin D. Roosevelt.

"The waters of this great river, instead of being wasted in the sea, will now be brought into use by man. Civilization advances with the practical application of knowledge in such structures as the one being built here in the pathway of one on the great rivers of the continent. The spread of its values in human happiness is beyond computation." —Herbert Hoover, November 1932 Jet Flow Gate Testing, June 1998 (Department of Interior Bureau of Reclamation) Hoover Dam was completed two years ahead of schedule and millions of dollars under budget. Over the years, investment in our nation’s infrastructure has fallen on the backburner, despite its importance for American citizens and our economy. The President has a plan to fix that, by reforming our programs and increasing funding to support our growing population and millions of jobs. It’s time to rebuild America. President Barack Obama views the Hoover Dam during a stop at the 1,900-foot long structure which spans the Colorado River at the Arizona-Nevada border, Oct. 2, 2012. (Official White House Photo by Pete Souza) Hoover Dam Hoover Dam Boulder City, NV Tourist Attractions - MapQuest See a problem? Let us know!

Hoover Dam, located about 30 miles southeast of Las Vegas, Nevada , is the most-visited dam in the world. Completed in 1935 with the intent of taming the Colorado River, the dam provides hydroelectric power to 1.3 million people and provides water to municipalities throughout the Southwest. Hoover Dam also created Lake Mead, the 16th largest man-made lake in the world, which provides a variety of outdoor recreation opportunities. If your travel sends you seeking American icons of ingenuity that combine man-made structures and nature, the Hoover Dam is a must-see. Parking and Public Transportation at Hoover Dam There is no public transportation to Hoover Dam, so driving or going on a chartered tour are your options. If you drive, you'll be able to drive right across the dam into Arizona; but since it is no longer open to through traffic, you're required to return to the Nevada side. A parking garage is available at the dam from 8 a.m. to 5:15 p.m. for a fee. Best and Worst Time to Go to Hoover Dam Hoover Dam is busiest in the summer months, so to avoid crowds schedule a visit before Memorial Day or after Labor Day.

The slowest months are January and February. Tours fill up early, so if you plan to take a guided tour offered by the dam's visitors' center, arrive early. The center opens at 9 a.m. daily and the first tour is at 9:25 a.m. Admission to Hoover Dam Children ages 3 and under are admitted free to the dam through the visitors' center. All others are charged admission -- adults, seniors, juniors and military personnel all pay the same price. Guided tours are available at additional fees. People who suffer from claustrophobia or who have a pacemaker or defibrillator should not take the tours, which are conducted in confined space among the power plant's generators that send out electromagnetic fields. Must See or Do at Hoover Dam Take a walk on the Mike O'Callaghan-Pat Tillman Memorial Bridge that allows for traffic to bypass the dam. As a pedestrian, you'll have incredible views of Lake Mead, the Colorado River and Hoover Dam (but you can't see the dam by driving across the bridge). For safety reasons, pedestrians are only allowed on the bridge during daylight hours.

Other Places to Visit Near Hoover Dam Pay a visit to the Arizona Hot Spring in Lake Mead National Recreation Area -- but go in the spring or fall because the hiking trails close in the summer due to extreme temperatures. Nearby Las Vegas offers a variety of dining and show opportunities as well as casino gambling. Insider Tip for Visitors to Hoover Dam Tours of Hoover Dam are not always available because of elevator malfunctions or maintenance, but the visitor center is open regardless. If you visit Hoover Dam during the busy summer months, dress for extreme heat and carry several bottles of water if you tour the dam. Author's bio: Ronna Pennington, historian and freelance journalist, left behind the editor's desk and newspaper industry after 20+ years to spend more time traveling with her family. Hoover Dam - Hoover Dam Las Vegas - Vegas Attractions | Vegas.com Cash, Mastercard, Visa, American Express and Discover. Hoover Dam description Named one of the Top 10 Construction Achievements of the 20th Century, Hoover Dam continues to draw crowds 80 years after its creation. Attracting more than a million visitors a year, Hoover Dam is located in Black Canyon, just minutes outside of Las Vegas.

On April 20, 1931, construction began on the Hoover Dam, the largest of its kind at the time. Despite the remote location and harsh working conditions, it was completed on March 1, 1936 in less than five years -- two years ahead of schedule -- and well under budget. The dam is named after America's 31st president, Herbert Hoover, who played a large role in bringing the nearby states into agreement about water allocations, settling a 25-year controversy. The dam has been called Boulder Canyon Dam as well as Boulder Dam, but Hoover Dam was reinstated as the official name by Congress in 1947. A National Historic Landmark, Hoover Dam is the highest concrete dam in the Western Hemisphere, standing at more than 725 feet above the Colorado River. With 17 generators producing 4 billion kilowatts of electricity a year, it also is one of the country's largest hydroelectric power facilities. Operation and maintenance of the facility are solely supported by revenue from power sales. Completed in October 2010, the Mike O' Callaghan -- Pat Tillman Memorial Bridge offers spectacular views that were once only available by helicopter.

For those who never fully appreciated the dam, it's hard not to become a fan after this. Visitors have access to drive to this bridge and see the dam from a high vantage point. Located about 1,500 feet south of the Hoover Dam, the walkway on the bridge is approximately 900 feet above the Colorado River. One neat fact is that visitors can go from Nevada to Arizona after crossing the 1,900-foot-long bridge. There are plenty of informative placards before and during the bridge walk. The construction of the bridge came to mind in the 1960s, but didn't actually happen until 40 years later. This bypass was created to not only reduce traffic, but also to protect Lake Mead and the Colorado River from hazardous spills and explosions. Two tours of the dam are available and well worth the time and money spent. For $11 per person (discounts available for children, seniors and active military) is the Hoover Dam Power Plant Tour. It is broken up into several components at numerous locations. The unique tour format allows guests to pick and choose which locations they want to see and the complete tour generally lasts about two hours.

The Hoover Dam Power Plant Tour begins with a brief video show depicting the history of Hoover Dam and how it came to be. Afterwards, a guide will escort you to an elevator for a 500-foot descent to get an up-close look at the power plant generators housed at the base of the dam. Guests will also see the original diversion tunnels and stand atop a giant, 30-foot pipe where they can feel the rumble of Colorado River water racing through it. Another interesting stop on the tour is an observation deck set above the dam affording panoramic views of the Colorado River and Lake Mead. The location also provides a bird's-eye view of the Hoover Dam facility, including an unobstructed look at the dam's mechanical components. The tour continues with several stops along the top of the dam, from the Winged Figures of the Republic to the Nevada Intake Tower. The second tour option is the new Dam Tour. For $30 per person visitors can enjoy all the options of the Power Plant Tour (including access to the visitor's center, observation deck and original Hoover Dam exhibit building), but they will also get to experience a unique and intimate tour of the dam itself.

The tour continues with an unprecedented look inside the dam, entering through the inspection tunnels. Visitors will be able to see inspection markings written on the walls from decades past and then peek out of the vents down onto the river below. After the inspection tunnels, guests will get to go deeper into the dam and see the seepage gallery and a set of antique stairs. This is the ultimate tour for those interested in the Hoover Dam. The view from the dam also offers a breathtaking look at Lake Mead, the country's largest man-made reservoir. Although water levels have been low recently, Lake Mead can store up to 9.2 trillion gallons of water, equal to two years of the river's annual flow. It also has become a popular recreation area, sought out by more than 9 million visitors each year. Note: At the Mike O' Callaghan -- Pat Tillman Memorial Bridge, there is limited parking reserved for visiting guests only. Those taking ground transportation tours to the Grand Canyon will be able to cross bridge, but not stop. Depending on the tour vehicle height, guests may not get a view of the Hoover Dam on the way back from the Grand Canyon.

View full description 81 Hoover Dam Access Rd, Boulder City, NV 89005 View the map

Question: The 'Hoover Dam' is onwhich American river?
Answer: COLORADO