Hoover Dam (Boulder Dam), a concrete arch-gravity dam in the Black Canyon of the Colorado River

Hoover Dam, one of the great accomplishments. Also known as Boulder Dam, is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between the U.S. states of Arizona and Nevada. When completed in 1935, it was both the world's largest electric-power generating station and the world's largest concrete structure. It was surpassed in both these respects by the Grand Coulee Dam in 1945. It is currently the world's 35th-largest hydroelectric generating station.

The Dam: At the time of construction, Hoover Dam was the largest in the world and although long since surpassed it is still an amazing structure and a marvel of engineering - a huge, curving wall of plain concrete 660 feet thick at the base and 726 feet high set between the vertical walls of Black Canyon, accompanied by strangely-angled pylons, cables, power generating plants and other machinery. In 1955, the dam was selected as one of the Seven Modern Engineering Wonders in the USA by the American Society of Civil Engineers, and it is was later designated a National Historic Landmark.

This dam, located 30 miles (48 km) southeast of Las Vegas, Nevada, is named after Herbert Hoover, who played an instrumental role in its construction, first as the Secretary of Commerce and then later as the President of the United States. Construction began in 1931 and was completed in 1935, more than two years ahead of schedule. The dam and the power plant are operated by the Bureau of Reclamation of the U.S. Department of the Interior. Listed on the National Register of Historic Places in 1981, Hoover Dam was designated a National Historic Landmark in 1985.
Lake Mead is the reservoir created behind the dam, named after Elwood Mead, who oversaw the construction of the dam.
Planning and agreements
A commission was formed in 1922 with a representative from each of the Basin states and one from the Federal Government. The federal representative was Herbert Hoover, then Secretary of Commerce under President Warren Harding. In January 1922, Hoover met with the state governors of Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming to work out an equitable arrangement for apportioning the waters of the Colorado River for their states' use. The resulting Colorado River Compact, signed on November 24, 1922, split the river basin into upper and lower halves with the states within each region deciding how the water would be divided. This agreement, known as the Hoover Compromise, paved the way for the Boulder Dam Project. This huge dam was built to help keep the silt and sediment out of the Colorado River, for flood control, and for hydroelectric-power generation
Power plant The hydroelectric generators at Hoover dam Following an uprating project from 1986 to 1993, the total gross power rating for the plant, including two 2.4 megawatt generators that power the plant's operations, is about 2080 megawatts.Excavation for the powerhouse was carried out simultaneously with the excavation for the dam foundation and abutments. Excavation for the U-shaped structure located at the downstream toe of the dam was completed in late 1933 with the first concrete placed in November 1933.

Generators at the Dam's Hoover Powerplant began transmission of electricity from the Colorado River to Los Angeles, California 266 miles (428 km) away on October 26, 1936. Additional generating units were added through 1961. Water flowing from Lake Mead through the gradually-narrowing penstocks to the powerhouse reaches a speed of about 85 miles per hour (137 km/h) by the time it reaches the turbines. The entire flow of the Colorado River passes through the turbines. The spillways are rarely used. Hydroelectric power plants have the ability to vary the amount of power generated, depending on the demand. Steam turbine power plants are not as easily "throttled" because of the amount of thermodynamic inertia contained in their systems.