Urban Social Structure

Commercial, industrial, and residential land uses are all important components of the structure of modern cities. Geographical research has led to the development of three basic models to explain the organization of space within cities.

Central Business Districts. Each of the urban-land-use models describes the location of urban activities relative to the central business district (CBD), which is the downtown retail, financial, and commercial heart of the city. Central business districts make up only a small percentage of the city's land area, but they have several important functions.

Banks, financial institutions, law firms, advertising agencies, and newspapers usually maintain their offices in CBDs. Location in the CBD facilitates face-to-face contact by professionals within and between companies. Government offices, courthouses, and other public buildings are also found in CBDs (Figure 10-11).

Figure 10-11 The Central Business District of San Francisco. The CBD of a city is dominated by stores, office buildings, and public institutions. Skyscrapers reflect the high value of office space near downtown

Prior to urban decentralization in the twentieth century, high-order retailing in North American cities was also concentrated in CBDs. Major department stores such as Macy's in New York, Jordan Marsh in Boston, and Woodward & Lothrop in Washington were located at the heart of their cities' CBDs, maximizing accessibility to potential customers.

Most major department stores are now located in suburban shopping malls, where they are more easily accessible to high-income customers. Other types of retail outlets remain prevalent in central cities, however. These include stores that sell highly specialized or exotic items, stores that cater to tourists visiting the CBD, and stores that cater to downtown office employees. Photocopying shops, dry cleaners, fast-food restaurants, printers, and office-supply shops are typical of the last category.

Despite the movement of major retail outlets from CBDs to suburbs, land values per unit area are highest in central cities, decreasing with increasing distance from the CBD (Figure 10-12). Central-city land values in such major cities as New York, London, and Los Angeles may be as high as several hundred million dollars per acre. Very high land values in association with the limited availability of central-city land has encouraged the development of skyscrapers. Skyscrapers increase the amount of available office and retail space near the city center.

Figure 10-12 Population Density, Land Values, and the City Center. In most cities, population densities, land values, and the concentration of urban land uses decline with increasing distance from the CBD

The three basic models of urban land use postulate different arrangements of commercial, industrial, and residential land use relative to one another (Figure 10-13). The concentric-zone model arranges industrial and residential land uses in rings around the city center. The CBD is at the center and is surrounded by industrial, low-income residential, middle-income residential, and high-income residential areas (Figure 10-13a).

Figure 10-13 The Internal Structure of Cities. The three classic models of the internal structure of cities are depicted here, illustrating the differences between them. Real cities combine elements of all three models, (a) The concentric zone model

By contrast, the sector model suggests that the residential neighborhoods are arranged in pie-shaped wedges or sectors around the centrally located commercial core (Figure 10—13b).

Figure 10-13 Continued, (b) The sector model

The third major model is known as the multiple nuclei model. This model differs from the others in that it is not based on the arrangement of residential areas around a commercial center (Figure 10-13c).

Figure 10-13 Continued, (c) The multiple-nuclei model

Rather, the city is seen to be composed of several commercial nuclei, with residential areas in between.