The United States has conducted more nuclear tests than the rest of the world, and was the first and only country to use a nuclear weapon in wartime. With the explosion of Trinity — the first nuclear bomb — in Alamagordo, New Mexico on July 16, 1945, the U.S. began the "nuclear weapons age." In subsequent years, the Soviet Union, Britain, France, China and India all followed suit. In 1996, Greenpeace offered this statistic: "Since July 1945, there have been 2,044 tests worldwide, the equivalent of one test occurring somewhere in the world every nine days for the last 50 years."

	Going Underground Before 1962, all U.S. nuclear tests were atmospheric, exposed to the atmosphere either on land or in the Pacific or Atlantic oceans, and were "grand operations, involving huge numbers of people, and each often with a set of clear objectives." With the first underground test of a nuclear explosive in September 1957 at the Nevada Test Site, testing took on a different, less public, character. The first underground test series was Operation Nougat in September 1961-April 1962. After 1962, no further atmospheric testing was conducted; from that point on, all explosive nuclear tests in the United States were underground. In accordance with the terms of the 1963 Limited Test Ban Treaty, complete containment of all nuclear weapons tests became the rule. However, in UNDER THE CLOUD: THE DECADES OF NUCLEAR TESTING, Richard Miller writes that complete containment is a myth, since so many tests leaked, including the notorious 1970 Baneberry shot, which spewed radioactive debris 10,000 feet into the skies. Baneberry was a 10 kiloton shot, about 2/3 the size of Hiroshima, and it was detonated 900 feet down. (View a photo of the Baneberry blast.) To accomplish underground testing, the test device is placed at the bottom of a vertically drilled hole or within a tunnel that is mined horizontally to a location deep enough to provide containment. Before tests are conducted, the Containment Evaluation Panel made up of scientists, engineers, and independent consultants must review containment design. Underground testing often leaves visible evidence on the surface in the form of subsidence craters or "sinks" of varying dimensions. Nevada Test Site The Nevada Test Site (NTS) is located in Nye County in southern Nevada, northwest of Las Vegas. The site spread across 1,350 square miles of federally owned land with restricted access. It is bordered on three sides by the Nellis Air Force Range, another federally restricted area, providing a buffer zone between the test area and public lands. The main U.S. nuclear testing ground, 100 atmospheric and 828 underground tests took place there between 1951 and 1992. Until 1951, U.S. nuclear weapons tests were conducted at distant islands in the Pacific Ocean. In the late 1940s, it was deemed more economical and practical for weapons to be tested within the continental boundaries of the U.S. A number of U.S. sites were considered on the basis of "low population density, safety, favorable year-round weather conditions, security, available labor sources, reasonable accessibility including transportation routes, and favorable geology." The NTS was originally selected to meet criteria for atmospheric tests, but subsequently was used for underground tests. At the end of 1992, the 928 nuclear tests left the Nevada Test Site pock-marked with subsidence craters, with test areas so heavily fractured that they are practically unusable for further testing. (View images of the Nevada Test Site.) Future Testing? On September 23, 1992, the U.S. conducted its last nuclear explosion test and joined France and Russia in moratoriums. The Hatfield-Exon-Mitchell amendment halted U.S. testing for a limited period of time. Read more about the United States and nuclear treaties. M. V. Ramana wrote in Pakistan's THE DAILY TIMES, 8/23/02: "Nuclear establishments around the world have tried to convince their citizens and others that these tests posed no risks to their health and the environment. However, even the limited amount of data that is available suggests that this is not the case. Testing of nuclear weapons has led to and would continue to cause damage to human health and the environment." In May of 1998, Pakistan announced that it had conducted five nuclear tests. Threats of testing elsewhere around the world still loom. In 2000, the U.S. Department of Energy published an unparalleled history of U.S. nuclear testing, "Origins of the Nevada Test Site," in which authors acknowledge the risks associated with developing a continental testing site: "What they did could not have been done lacking a dire threat or, equally important, a national consensus that the nation's security took precedence over personal inconvenience. What they did could not be done today. Successfully locating and using in a matter of weeks, without public knowledge and referendum, a facility whose activities would cause physical damage in nearby communities and spread a known harmful substance across vast swaths of the countryside is now simply inconceivable." Despite the potential dangers, the Nevada Test Site has maintained a readiness to test nuclear weapons underground within 24-36 months. The Bush administration, in the Department of Energy's Fiscal Year 2004 budget request, asked for $25 million in funding to enhance test readiness to 18 months. Sources: AtomicArchive.com; Council for a Livable World; GlobalSecurity.org; The Nuclear Weapon Archive