Major Functional Regions of the United States South

Major Functional Regions of the United States South James E. Lewis * How and by what means does man organize area to suit his purposes best? For a considerable length of time, certainly since the days of Johann von Thiinen in the early nineteenth century, research workers have been seeking answers to this question in diverse portions of the earth surface. An examination of pertinent literature combined with considerable field observation has led the author to conclude that the key elements in man's organization of area are urban places and circulation. (1) That is to say, circulation networks provide the linkages between an urban place and the population of the surrounding area, linkages which are essential to the maintenance of this areal organization. Functional regions are defined here as areas integrated by these circulation linkages between an urban place and the population of the surrounding area. The purpose of this study is to demonstrate this point by delimiting major functional regions for the United States South. SELECTION OF THE REGIONAL NODES. The first step in the preparation of a map of functional regions is generally the selection of the regional nodes. Usually this is accomplished by selecting some item or items as a measure of the relative importance of urban places in terms of service functions. Population size, number of retail stores, volume of retail and wholesale trade, and newspaper circulation are representative of the indices that have been used. Almost without exception the nodes selected have been those centers possessing values above a specified threshold. In this study, however, selection of the regional nodes was based on the examination of highway traffic flow maps. Points of absolute minimum traffic flow were located on the maps, and the cities between which these points occurred were identified as regional nodes. This technique permits identification of regional nodes that cannot be identified on the basis of purely statistical data because of their low relative rank. Conversely, some centers that rank high in the statistics may not be major focal points for the highway traffic generated by the population of the surrounding areas. Twenty-six major regional nodes were identified. In most cases it was relatively easy to select the one city that represented the regional node. In two cases, however, more than one major urban place constituted the regional node. Hence, Tampa-St. Petersburg, Florida, and BrownsvilleHarlingen -San Benito, Texas, were designated as regional nodes. DELIMITATION OF THE FUNCTIONAL REGIONS. The functional regions of the United States South were delimited in accordance with a theoretical technique based on the gravity model of human interaction. The model employed in this study incorporated two measures which ap- *Dr. Lewis is assistant professor of geography at Louisiana State University, Baton Rouge. The paper was accepted for publication in June 1967. 2 The Southeastern Geographer pear to indicate the interrelationship of city and region. First, an Index of Regional Centrality was computed. This measure is composed of the following selected indicators of centrality: (1) population, (2) employment in retail trade, (3) employment in wholesaling establishments, and (4) employment in selected services. In general, the regional functions of large urban places are proportional in number and variety to the population of the place. The three remaining indicators are introduced for the purpose of refining the gross relationships, represented by population alone. The retail, wholesale, and service functions of urban places are their most direct links with the population of the surrounding area. The retail function links the urban place with individuals , the wholesale function links the urban place with business enterprises in other urban places, and the ser\'ice function links the urban place with both individuals and business enterprises. These measures Avere combined into an Index of Regional Centrality according to the folloAving procedure. The index number for each component was computed by setting the values for Atlanta, Georgia, equal to one hundred. Any city could have been selected for this purpose. It was known, hoAvever, that Atlanta would fall in the upper part of the group and, hence, the magnitude of the index values would be held at a reasonable level. The index values were summed and averaged. The average index values were considered to...