The Nevada National Security Site, known as the Nevada Test Site until August 23, 2010, is a United States Department of Energy reservation located in southeastern Nye County, Nevada, about 65 miles northwest of the city of Las Vegas. Formerly known as the Nevada Proving Grounds, the site was established on January 11, 1951 for the testing of nuclear devices, covering approximately 1,360 square miles of desert and mountainous terrain. Nuclear weapons testing at the Nevada Test Site began with a 1-kiloton-of-TNT bomb dropped on Frenchman Flat on January 27, 1951. Over the subsequent four decades, over one thousand nuclear explosions were detonated at the NTS. Many of the iconic images of the nuclear era come from the NTS. NNSS is operated by Mission Support and Test Services, LLC.
During the 1950s, the mushroom clouds from the 100 atmospheric tests could be seen from almost 100 mi away. The city of Las Vegas experienced noticeable seismic effects, and the mushroom clouds, which could be seen from the downtown hotels, became tourist attractions. St. George, Utah received the brunt of the fallout from above-ground nuclear testing in the Yucca Flats/Nevada Test Site.