Nevada National Security Site

 military, nuclear testing area, proving ground

The Nevada Security Site (formerly known as the Nevada Proving Ground and later the Nevada Test Site NTS) is a United States Department of Energy reservation located in Nye County, Nevada, about 65 miles (105 km) northwest of the City of Las Vegas. The site, established on January 11, 1951 for the testing of nuclear weapons, is composed of approximately 1,350 square miles (3,500 km²) of desert and mountainous terrain. Nuclear testing at the Nevada Test Site began with a one-kiloton (4 terajoule) bomb dropped on Frenchman Flat on January 27, 1951. Many of the iconic images of the nuclear era come from NTS.

Nuclear testing at the NTS was conducted in two distinct eras: the atmospheric testing era (January 1951 through October 1958) and the underground testing era (1961 to 1992). On 31 October 1958, the United States and the Soviet Union entered into voluntary test moratoria which lasted until the USSR. resumed testing on 01 September 1961. The United States responded with renewed testing on 15 September 1961. A few surface, near surface, and cratering tests were conducted from 1961 to 1968, but all other nuclear weapons tests have been carried out underground since 1961. The United States and the Soviet Union signed the Limited Test Ban Treaty on 05 August 1963, which banned testing nuclear weapons in the atmosphere, in outer space and underwater.
The United States conducted 119 nuclear tests at the NTS from the start of testing in January 1951 through October 1958. Most of those nuclear tests were carried out in the atmosphere. Some tests were positioned for firing by airdrop, but metal towers were used for many Nevada tests at heights ranging from 100 to 700 feet (30-200 meters) above the ground surface. In 1957 and 1958, helium-filled balloons, tethered to precise heights and locations 340 to 1,500 feet (105 to 500 meters) above ground, provided a simpler, quicker, and less expensive method for the testing of many experimental devices. The tests of the atmospheric era took place in Yucca and Frenchman Flats. The 119 nuclear tests that were conducted at the NTS during the atmospheric testing era (1951-1958) consist of 97 nuclear tests conducted in the atmosphere, of two cratering tests, detonated at depths less than 100 feet (30 meters), and of 20 underground tests.
In 1962, before the onset of the Limited Test Ban Treaty, the United States conducted, in addition to its underground tests, two small surface tests, one tower test and two cratering tests as part of the nuclear weapons testing program. Six nuclear cratering tests were conducted from 1962 through 1968 as part of the peaceful applications (Plowshare) program. The overwhelming majority of the 809 tests that took place at the NTS from 1961 through September 1992 were conducted underground either in shafts or in tunnels that were designed for containment of the radioactive debris. Most underground tests were conducted under Yucca Flat but a few underground round and cratering tests took place under Buckboard, Pahute, and Rainier Mesas in the northern part of the Nevada Test Site.
The site is covered with subsidence craters from the testing. The Nevada Test Site was the primary testing location of American nuclear devices; 129 tests were conducted elsewhere (many at the Pacific Proving Grounds in the Marshall Islands).
During the 1950s, the mushroom cloud from these tests could be seen for almost 100 miles in either direction, including the city of Las Vegas, where the tests became tourist attractions. Americans headed for Las Vegas to witness the distant mushroom clouds that could be seen from the downtown hotels.

On July 17, 1962 the test shot "Little Feller I" of Operation Sunbeam became the last atmospheric test detonation at the Nevada Test Site. Underground testing of weapons continued until September 23, 1992, and although the United States did not ratify the Comprehensive Test Ban Treaty, the articles of the treaty are nevertheless honored and further tests have not occurred. Tests not involving the full creation of a critical mass ("sub-critical" testing) continue.
One notable test shot was the "Sedan" shot of Operation Storax, a 104 kiloton shot for the Operation Plowshare which sought to prove that nuclear weapons could be used for peaceful means in creating bays or canals—it created a crater 1,280 feet (390 m) wide and 320 feet (100 m) deep that can still be seen today. While most of the larger tests were conducted elsewhere, NTS was home to tests in the 500 kiloton to 1 megaton (2 to 4 petajoule) range, which caused noticeable seismic effects in Las Vegas.