The Spatial Structure of Cities in the United States

In recent years, the spatial structure of cities has become the subject of considerable interest, as travel behavior, greenhouse gas emissions, loss of habitat, public expenditures, and more are thought to be influenced by the spatial structure of cities. In this paper we examine the spatial structure of 35 metropolitan areas in the United States. Based on the 2010 Census data, we focus on the distributions of populations in metropolitan areas in 2010 and on changes between 1990 and 2010. Specifically, we examine population levels and population density at the metropolitan, urbanized area, principal city, and census block levels. We also examine how much growth has occurred since 1990 in previously urbanized areas, in newly urbanized areas, and in never urbanized areas. Finally, we examine the spatial distribution of populations within urban areas, exploring the extent to which population is concentrated within subareas and the extent to which population density declines with distance from the city center. We find that significant differences in recent growth patterns remain between the older and more densely developed cities of the Northeast and cities in the South and West. Most urban growth is now occurring in cities in the South and West, causing them to experience increases in density in their principal cities, urbanized area, and nonurbanized areas. We also find, however, that much of the population growth in the largest metropolitan areas of the United States continues to occur at the urban fringe, causing overall densities to decline, density gradients to flatten, and measures of concentration to fall.