<Tr> <Th_colspan="2"> Test information </Th> </Tr> <Tr> <Th> Nuclear tests </Th> <Td> 928 </Td> </Tr> <P> The Nevada National Security Site (N2S2), (though the abbreviation NNSS is still used), 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 km) of desert and mountainous terrain . Nuclear weapons 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 . NNSS is operated by National Security Technologies, LLC, a joint venture of Northrop Grumman, AECOM, CH2M Hill, and Babcock & Wilcox . </P> <P> 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--828 of the 928 total nuclear tests--were underground . </P>

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