been stepped up, and it became clear that the program would require more frequent tests than could be conducted feasibly in the Pacific. The rate of development of new and improved nuclear weapons depended on whether or not a continental site could be utilized. ‘ \ Available locations were surveyed again and checked against criteria such as: density of population; weather, particularly for its effects on radiological safety locally and nationally; opera- tional estate then a Range, site. ' factors such as air lanes, labor pool, transportation; real available to the government; and security. The Nevada site, portion of the Air Force's Las Vegas Bombing and Gunnery most nearly satisfied all of the criteria for a continental . Careful review of all available research and test data relating to fallout and-to blast indicated that under the controls planned, relatively low power tests could be fired with adequate assurance of public safety. , The decision to establish a continental test site was made in December, 1950, and the Nevada Test Site was first used for an atomic test on January 27,-1951. Numbers and Types of Detonations Forty-five weapons, weapon prototypes, or experimental devices were fired in five series in Nevada between January 27, 1951, and May 15, 1955. All were relatively small in yield, ranging from less than one kiloton (equal to 1,000 tons.of TNT) to considerably less than 100 kilotons. These yields may be compared with the tremendous explosive force of the larger weapons.or devices included among those tested in the Pacific, with ranges having been announced of up to about 500 kilotons for fission bombs and up.to millions of tons (megatons) for thermonuclear devices. Of the 45 detonations, 22 were tower placements, 19 were air drops, three were surface or underground placements, and one was a 280 millimeter cannon shot. The details of detonations by series and by shots are given in a chart at the front of this compilation. Uses Made of Individual Nevada Tests A sizeable majority of the shots have been primarily developmental, of devices conceived by scientists in the Los Alamos Scien- tific Laboratory and the University of California Radiation Labora- tory branch at Livermore, and constructed by those laboratories with the assistance of Sandia Laboratory. Los Alamos devices have been tested in all series, while Livermore entered the continental testing program in the spring 1953 series. CORTED/ Dog ?