An assumption that underlies most discussions of electric facility sitting is that the initial selection of a site is the responsibility of the utility concerned-subject to governmental review and approval only after the site has been chosen. This assumption must be changed so that site selection becomes a joint responsibility of the utilities and the appropriate governmental authorities from the outset. Sitting decisions would be made in accordance with either of two strategies. The metropolitan strategy takes the existing distribution of population and supporting facilities as given. An attempt is then made to choose between, scattered or concentrated sitting and to locate generating facilities in accordance with some economic principle. For example, the economic objectives of least-cost construction and rapid start-up may be achieved, in part, by a metropolitan strategy which takes advantage of existing elements of social and physical infrastructure in the big cities. Under the frontier strategy ,the energy park may be taken as an independent variable, subject to manipulation policy-makers as a means of achieving desired demographic(人口统计学的)or social goals, such as rural-town-city mix. Thus, population distribution is taken as a goal of national social policy, not as a given of a national energy policy. In the frontier Strategy, the option of dispersed sitting is irrelevant to the standpoint of community impact because there is no pre-existing community of any size. Traditionally, the resource-environment of a location-and especially its situation relative to the primary industry of the inland areas-has had a special importance in American history. In the early agricultural period, the most valued natural endowment was arable land with good climate and available water. American's oldest cities were mercantile outposts of such agricultural areas. Deep-water ports developed to serve the agricultural inland areas, which produced staple commodities in demand on the world market. From the 1840s onward the American manufacturing heartland developed westwards to encompass Lake Superior iron ores, the Pennsylvania coalfields, and the Northeast's financial, entrepreneurial, and manufacturing roles. Subsequent metropolitan growth has been organized around this national core. The frontier strategy implements the principle of created opportunity and this helps explain why some environmentalists perceive the energy park idea as a threat to nature. But the problems, of modern society, no matter with or without energy parks, require ever more comprehensive planning. And energy parks are a means of advancing American social history rather than merely responding to power needs in an unplanned, aimless manner. It is implied in the passage that in selecting a site for past electric facilities ______.