The Nevada National Security Site (NNSS), previously the Nevada Test Site (NTS), is a United States Department of Energy reservation located in southeastern Nye County, Nevada, about 65 miles (105 km) northwest of the city of Las Vegas.

Formerly known as the Nevada Proving Grounds, the site was established on 11 January 1951 for the testing of nuclear devices, covering approximately 1,360 square miles (3,500 km2) of desert and mountainous terrain. Nuclear testing at the Nevada Test Site began with a 1-kiloton-of-TNT (4.2 TJ) bomb dropped on Frenchman Flat on 27 January 1951. Many of the iconic images of the nuclear era come from the NTS.

During the 1950s, the mushroom clouds from the 100 atmospheric tests could be seen for almost 100 mi (160 km). The city of Las Vegas experienced noticeable seismic effects, and the distant mushroom clouds, which could be seen from the downtown hotels, became tourist attractions. St. George, Utah, received the brunt of the fallout of above-ground nuclear testing in the Yucca Flats/Nevada Test Site. Winds routinely carried the fallout of these tests directly through St. George and southern Utah. Marked increases in cancers, such as leukemia, lymphoma, thyroid cancer, breast cancer, melanoma, bone cancer, brain tumors, and gastrointestinal tract cancers, were reported from the mid-1950s through 1980. The vast majority of nuclear tests, 828 in all, were underground.

From 1986 through 1994, two years after the United States put a hold on full-scale nuclear weapons testing, 536 anti-nuclear protests were held at the Nevada Test Site involving 37,488 participants and 15,740 arrests, according to government records.

Those arrested included the astronomer Carl Sagan and the actors Kris Kristofferson, Martin Sheen, and Robert Blake.

The Nevada Test Site contains 28 areas, 1,100 buildings, 400 miles (640 km) of paved roads, 300 miles of unpaved roads, ten heliports, and two airstrips.

The test site offers monthly public tours, often fully booked months in advance. Visitors are not allowed to bring in cameras, binoculars, or cell phones, nor are they permitted to pick up rocks for souvenirs.

While there are no longer any explosive tests of nuclear weapons at the site, there is still subcritical testing, used to determine the viability of the United States' aging nuclear arsenal. Additionally, the site is the location of the Area 5 Radioactive Waste Management Complex, which sorts and stores low-level radioactive waste that is not transuranic and has a half life not longer than 20 years. Bechtel Nevada Corporation (a joint venture of Lockheed Martin, Bechtel, and Johnson Controls) ran this complex until 2006. Several other companies won the bid for the contract since and combined to form a new company called National Security Technologies, LLC (a joint venture of Northrop Grumman, AECOM, CH2M Hill, and Nuclear Fuel Services). AECOM, known earlier as Holmes and Narver, held the Nevada Test Site contract for many years before Bechtel Nevada Corp. had it.

The Radiological/Nuclear WMD Incident Exercise Site (T-1), which replicates multiple terrorist radiological incidents with train, plane, automobile, truck, and helicopter props is located in Area 1, at the former site of tests EASY, SIMON, APPLE-2, and GALILEO.

en.wikipedia.org/wiki/Nevada_Test_Site