It is assumed that large concentrations of industry and people will be major enemy targets for attack with nuclear weapons. The atomic bomb and chemical warfare are weapons of mass destruction most efficiently used on large targets, such as our standard metropolitan areas, with their high concentrations of population and industry. Biological warfare can be efficiently used against both urban and rural areas and populations. Based on Census Bureau and Department of Labor statistics, there has been drawn up a list of 193 potential atomic target areas in the continental United States, the Territories and possessions, including State and Territorial capitals which do not qualify as standard metropolitan areas. Of the 193 areas, the 70 which contain the highest concentrations of both industry and population are designated 'critical target areas,'since they are assumed to be the most likely targets.... Nearly half the population of the United States lives within these 70 areas, although they comprise less than 3 percent of the total area of the Nation". (FCDA, 1953 Annual Report, 10)