AP Human Geography


: the process by which towns and cities are formed and become larger as more and more people begin living and working in central areas

Why is Urbanization important?

Urban Structure Models

"Cities are not simply random collections of buildings and people. They exhibit functional structure: they are spatially organized to perform their functions as places of commerce, production, education, and much more. One of the most important forces determining where certain buildings or activities are located within a city deals with the price of land. This tends to be the highest in the downtown area and declines as one moves outward from the center. The United States is the only country in the world in which the majority of the people live in the suburbs. Even though house prices may be higher in the suburbs, the land value is lower (a downtown apartment complex will produce much more revenue per year than a few suburban homes occupying the same amount of space). In every other country the majority resides in either rural or urban areas."


The central business district (CBD) (or “downtown”) is the core of the city. High land values, tall buildings, busy traffic, converging highways, and mass transit systems (e.g., South Florida’s “Tri-Rail”) mark the American or European CBD.

Concentric Zone Model

Developed by Ernest Burgess

Burgess recognized five concentric functional zones.

At the center was the CBD (1). The zone of transition (2) was characterized by residential deterioration and encroachment by business and light manufacturing. The zone of independent workers’ homes (3) was primarily occupied by the bluecollar (wage-earners, manual laborers) labor force. The zone of better residences (4) consisted mainly of the middle-class. Finally, the commuters’ zone (5) was the suburban ring, consisting mostly of white-collar workers who could afford to live further from the CBD. This model was dynamic. As the city grew, the inner zones encroached on the outer ones.

Hoyt's Sector Model

In the late 1930s, Homer Hoyt’s sector model (B) was published, partly as an answer to the drawbacks of Burgess’ concentric zone model. As technology dealing with transportation and communication was improving, growth alone created more of a pie-shaped urban structure. Hoyt discovered that land rent (for residential, commercial, or industrial) could remain consistent all the way from the CBD to the city’s outer edge.

Multiple Nuclei Model

In the 1940s, Chauncy Harris and Edward Ullman, arguing that neither of the earlier models adequately reflected city structure, proposed the multiple nuclei model (C). This model was based on the notion the CBD was losing its dominant position and primacy as the nucleus of the urban area. Several of the urban regions would have their own subsidiary but competing “nuclei.” As manufacturing cities became modern cities and modern cities became increasingly complex, these models became less and less accurate.

Urban Realms Model

Today, there are urban realms, components of giant conurbations (connected urban areas) that function separately in certain ways but are linked together in a greater metropolitan sphere. In the early postwar period (1950s), rapid population diffusion to the outer suburbs created distant nuclei, but also reduced the volume and level, of interaction between the central city and these emerging suburban cities. By the 1970s, outer cities were becoming increasingly independent of the CBD to which these former suburbs had once been closely tied. Regional shopping centers (e.g., malls) in the suburban zone were becoming the new CBDs of the outer nuclei.

Edge Cities

Coined by Washington Post journalist and author Joel Garreau in 1991.

Garreau equates the growing edge cities at major suburban freeway interchanges around America as the latest transformation of how we live and work. These new suburban cities have sprung up like dandelions across the fruited plain, they're home to glistening office towers, huge retail complexes, and are always located close to major highways.

Central Place Theory

Coined by German geographer Walter Christaller 1933 after he began to recognize the economic relationships between cities and their hinterlands (areas farther away).

Central place theory is a spatial theory in urban geography that attempts to explain the reasons behind the distribution patterns, size, and number of cities and towns around the world. It also attempts to provide a framework by which those areas can be studied both for historic reasons and for the locational patterns of areas today.