Multicolored maps of Los Angeles, San Francisco, and Tampa, denoting neighborhood fragmentation
Neighborhood fragmentation of Los Angeles, San Francisco, and Tampa. Urban Science/Creative Commons license

Yet in cities, affluent white neighborhoods and high-poverty black ones are outliers, resisting the fragmentation shown with other types of neighborhoods.

America’s cities have changed considerably over the past half century, in ways that challenge and confound our theories for understanding them.

Back in the early 20th century, the urban theorists associated with the Chicago School—Robert Park, Ernest Burgess, Homer Hoyt, and others—laid out the basic model which still shapes the way we think about cities. Cities are formed around a dense, commercial core. Surrounding that core is a warehousing, logistics, and food-servicing area: neighborhoods like New York’s Chelsea, Meatpacking District, Soho, and Tribeca, which are now rife with gentrification. As you move further out, dense multifamily housing areas eventually give way to suburban residential districts with lower and lower densities, filled with more affluent residents living in greener and tonier neighborhoods.

But during the 1960s and 70s, America saw the rise of much more sprawling Sunbelt cities. They did not form in such a concentric fashion, instead developing around multiple cores in a poly-centric shape. Starting around 2000, a large and growing number of places have seen a powerful back-to-the-city movement of affluent and educated people.

The question all of this raises: What do our metropolitan areas look like—what shape, or model, best describes them—today?

That is the question that forms the heart of a new study by Elizabeth Delmelle, a professor of geography and earth sciences at the University of North Carolina, Charlotte. To get at it, Delmelle looks at the various types of neighborhoods and the patterns in which those neighborhoods fit together in the nation’s 50 largest metro areas. She defined these neighborhood types based on an analysis of 18 different variables, including income levels, education, poverty, homeowners versus renters, home values, type of housing stock, race, and more. Based on this, she identified nine distinct types of neighborhoods that form the modern metropolis:

1. Wealthy, white, educated
2. Newer single-family homes, largely white, high socioeconomic status
3. White and Asian, multiunit housing, educated, recent in-movers, high-home values
4. Older homes, white, some Hispanic, blue-collar workers
5. Hispanic and black, higher poverty, deteriorating, older, single-family homes
6. Black, high poverty, vacant homes
7. Hispanic and foreign born, high poverty, single-family homes
8. Mixed race, average socioeconomic status, renters
9. Asian, foreign born, multiunit homes, high poverty, recent in-movers

Her study examines the way these nine types of neighborhoods fit together to shape today’s metropolis. If these neighborhoods line up neatly together, the form of cities and metro areas can be considered orderly. But if they are mixed in a patchwork configuration, that form can be considered to be more fragmented. She used a metric called “patch fragmentation,” in which a contiguous set of census tracts belong to the same neighborhood class. Next, she employed a measure of “edge density” to see if these neighborhood types have neat borders or more complex shapes with a “ragged edge.” She tracks changes in this spatial patterning from 1990 to 2010, a 20-year period of substantial gentrification and back-to-the city movement.

What she finds is striking. America’s cities and metro areas bear little resemblance to the urban/suburban or poor city/rich suburban model of the past. But neither do they look like the inverted pattern of rich, urban centers surrounded by poorer suburbs that some say is a consequence of the gentrified city. Instead, the modern metropolis takes the form of a patchwork of polygons, a chaotic and jumbled mixture of neighborhood types. This can be seen in the maps below, which show how these nine neighborhood types line up in three key metropolitan areas. For example, in the core of Los Angeles, moving over just one census tract can mean entering an entirely different neighborhood.

Neighborhood Fragmentation of Los Angeles, San Francisco, and Tampa, 2010

Source: Urban Science, Creative Commons license

There has been a significant decrease in the clustering of neighborhood types, and thus an increase in the fragmentation of America’s leading metros over this period. This is true of superstar cities—Los Angeles has the most fragmented pattern of any metro, followed by New York and San Francisco. Smaller cities also faced increasing fragmentation—led by Tampa, Philadelphia, Boston, Hartford, Baltimore, Providence, Miami, Cleveland, Washington, D.C., Detroit, and Milwaukee—at increasing rates. The only metro that did not see a rise in fragmentation is New Orleans, whose neighborhood landscape was massively altered in 2005 by Hurricane Katrina.

Change in Metropolitan Fragmentation, 1990 to 2010

Source: Urban Science, Creative Commons license

Beneath this growing geographic diversity of the American city and metropolis lies several important trends.

The suburbs are becoming far more diverse along racial, ethnic, and class lines. The traditional perception—and to some extent, the reality—of suburbs as middle-class, white, and filled with single-family homes is giving way to communities which are far more diverse. While urbanists focus attention on gentrifying cities and the transformation of urban centers, the suburbs are in the midst of dramatic change, showing striking ethnic, racial, and socio-economic variety and becoming havens for immigrants. Suburbs also now share the problems of chronic poverty and class division that were once thought to be the province of the inner city.

While in cities, many of the new urban residents fit a stereotypical image of a highly educated, white gentrifier—and it’s true that affluent whites have flocked back to the city in record numbers—the ongoing transformation of urban areas is far more complex and varied. Some transformation is driven by the influx of the white and the wealthy, but urban change can also be driven by racial and ethnic minorities, immigrants, and less advantaged groups moving across the city. Not only are expensive, coastal, superstar cities dramatically changing, but so are younger and less expensive Western and Southern cities. A changing urban landscape is not just the province of highly educated whites, but of a more diverse group of residents.

But there are two types of neighborhoods that remain largely unchanged, forming a disturbing duality that continues to underpin America’s reconfigured metropolis. Even as our cities have morphed into a patchwork of different types of neighborhoods, a stark geographic divide remains across race and class lines.

Echoing and reinforcing the findings of sociologists like William Julius Wilson, Robert Sampson, and Patrick Sharkey, Delmelle’s research shows that areas of concentrated black poverty (neighborhood type six) remain the most persistent neighborhood type. Juxtaposed to this is the similarly persistent concentration of the affluent and advantaged white and Asian residents, spanning both suburban and urban areas (type three). This geographic divide along race and class lines is most acute in the superstar cities of New York and Los Angeles, Delmelle finds.

Across the 50 metro areas, Delmelle found neighborhood types six and three to be the most persistent to fragmenting. Only in New York did Delmelle find the high-poverty Hispanic neighborhood (type seven) to be equally persistent and clustered. Even in Los Angeles, the high-poverty Hispanic neighborhoods have fragmented and intermixed with the high-poverty Asian neighborhoods (type nine).

As the urban and suburban “middle” of our geography undergoes radical transformation, becoming more diverse and intermixed, the polar opposites of geographic advantage and disadvantage remain largely the same, reflecting long-standing divides of race and class.

CityLab editorial fellow Claire Tran contributed research and editorial assistance to this article.

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