Lake Mead is the largest reservoir

Reservoir

A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...

 in the United States. It is located on the Colorado River about 30 mi (48.3 km) southeast of Las Vegas

Las Vegas, Nevada

Las Vegas is the most populous city in the U.S. state of Nevada and is also the county seat of Clark County, Nevada. Las Vegas is an internationally renowned major resort city for gambling, shopping, and fine dining. The city bills itself as The Entertainment Capital of the World, and is famous...

, Nevada, in the states of Nevada and Arizona

Arizona

Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...

. Formed by water impounded by the Hoover Dam

Hoover Dam

Hoover Dam, once known as Boulder Dam, is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between the US states of Arizona and Nevada. It was constructed between 1931 and 1936 during the Great Depression and was dedicated on September 30, 1935, by President...

, it extends 112 miles (180.2 km) behind the dam, holding approximately 28500000 acre.ft of water.
The lake was named after Elwood Mead

Elwood Mead

Elwood Mead was a professor, politician and engineer, known for heading the Bureau of Reclamation from 1924 until his death in 1936. During his tenure, he oversaw some of the most complex projects the Bureau of Reclamation has undertaken...

 (1858–1936), who was the commissioner of the U.S. Bureau of Reclamation from 1924 to 1936 during the planning and construction of the Boulder Canyon Project that created the dam

Dam

A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

 and lake.