Urban Spatial Structure

In economically advanced, postindustrial countries such as the United States, the proportion of people living in towns, cities, and metropolitan areas reached 75% or more by the late 20th century in developed countries. In the world as a whole, the proportion of urban population rose from less than 5% in 1800 to slightly more than 50% of a much larger aggregate world population by the early 21st century. Numerically, world urban residents expanded from perhaps 30 million in 1800 to about 3 billion in 2000. Matters of urban spatial structure, which pertain to the geographical patterns and characteristics of urban places, thus concern a very large and expanding share of the world's people. This entry examines the factors that influence urban spatial structure and how they contributed to growth in urbanization in the United States. It then discusses the ways in which geographers have conceptualized urban spatial structure through the concentric zone, sector, and multiple-nuclei models and also considers the limitations of these models. The entry concludes with a look at how urban spatial structure may evolve in the future.

One major facet of urban spatial structure involves the overall geographical patterns of urban settlements at regional, national, and global scales, especially in terms of the sizes and locations of towns, cities, and metropolitan areas. Another major facet involves the internal spatial arrangements of activities and land uses within urban settlements. Indeed, one of the most common analytical distinctions made in urban geography reflects a division according to geographical scale into matters that involve, first, “interurban” features of “systems of cities” for cartographically smaller map scales, at which towns, cities, or metropolitan areas are most reasonably represented using point symbols, and, second, “intra-urban” characteristics of city systems for cartographically larger map scales, at which the internal features of towns, cities, or metropolitan areas are most reasonably represented using line or area symbols. In between these are intermediate geographical scales, at which urban land use and activity patterns can be examined for metropolitan regions, which are conventionally subdivided into central city, suburban, and fringe subareas.