Concentric Zone Model

Concentric Zone Model Definition

Most US cities have similar growth patterns, as many of them spread from their original cores outward. Ernest Burgess (1886-1966) noticed this in the 1920s and came up with a dynamic model to describe and predict how cities grew and what elements of the city would be found where.

The Concentric Zone Model was based essentially on Burgess's observations, principally in Chicago (see below), that mobility is directly related to land value. By mobility, we mean the number of people who pass by a given location on an average day. The greater the number of people who pass by, the more opportunities there are to sell them products, which means that more profit will be made there. More profit means higher commercial land value (expressed in terms of rent).

Other than neighborhood businesses in the 1920s, when the model was devised, the greatest concentration of consumers occurred in the center of any US city. As you moved outward from the center, commercial land values dropped, and other uses took over: industrial, then residential.

Burgess Concentric Zone Model

The Burgess Concentric Zone Model (CZM) can be visualized using a simplified, color-coded diagram.

Fig. 1 - Concentric Zone Model. Zones from innermost to outermost are CBD; factory zone; zone of transition; working-class zone; residential zone; and commuter zone

CBD (Central Business District)

The core of the US city is where it was founded, usually at the junction of two or more transport routes, including roads, rails, rivers, lakefront, sea coast, or a combination. It contains the headquarters of major companies, major retailers, museums and other cultural attractions, restaurants, government buildings, large churches, and other establishments that can afford the most expensive real estate in the city. In the CZM, the CBD continually expands as the city grows in population (as most cities were doing in the first part of the 20th century, particularly Chicago, the original model).

Fig. 2 - The Loop, Chicago's CBD, flanks both sides of the Chicago River

Factory Zone

The industrial zone is located in the first ring out from the CBD. Factories do not need high consumer traffic, but they do need direct access to transport hubs and workers. But the factory zone is not stable: in the CZM, as the city grows, the factories are displaced by the growing CBD, so they are in turn displaced into the zone of transition.

Zone of Transition

The zone of transition juxtaposes factories that the CBD has displaced from the factory zone and the most impoverished neighborhoods. Rents are the lowest in the city because of the pollution and contamination caused by the factories and because no one of any means wishes to live in places that are almost entirely rental, as they will be demolished as factories expand into the area. This zone contains first-generation immigrants from abroad as well as from impoverished rural regions of the US. It provides the cheapest labor source for the CBD's tertiary sector service jobs and the factory zone's secondary sector jobs. Today, this zone is called the "inner city."

The zone of transition is also continuously expanding, displacing people from the next zone.

Working Class Zone

As soon as immigrants have the means, perhaps after the first generation, they move out of the zone of transition and into the working class zone. Rents are modest, there is a fair amount of home ownership, and most of the problems associated with the inner city are gone. The trade-off is a longer commute time. This zone, in turn, expands as it is pushed by the inner rings of the CZM.

Fig. 3 - Tacony in the 1930s, located in the Residential Zone and later the Working Class Zone of Philadelphia, PA

Residential Zone

This zone is characterized by the middle class and is composed almost entirely of homeowners. It comprises second-generation immigrants and many people who move to the city for white-collar jobs. It is expanding on its outer edge as its inner edge is taken over by the growth of the working class zone.

Commuter Zone

The outermost ring is the streetcar suburbs. In the 1920s, most people still commuted by train, so suburbs located a half hour or more from downtown were expensive to get to but provided exclusivity and better quality of life for people of financial means. They were far from the polluted downtown and crime-ridden inner-city areas. Inevitably, as the inner zones pushed outward, this zone expanded farther and farther into the countryside.

Concentric Zone Model Strengths and Weaknesses

The CZM has been widely criticized for its limitations, but it also has some benefits.

Strengths

The CZM does capture the primary form of the US city of the first half of the 20th century. It was characterized by explosive growth due to immigration on a scale rarely seen elsewhere in the world. The model caught the imagination of sociologists, geographers, planners, and others as they sought to understand and control what was happening in the US's metropolises.

The CZM provided a blueprint for urban models that was followed a few years later by the Hoyt Sector Model, then by the Multiple-Nuclei Model, both of which built upon the CZM as they tried to take into account what the automobile was doing to US cities. The culmination of this process were concepts such as Edge Cities, the Megalopolis, and the Galactic City Model, as successive generations of geographers tried to describe the seemingly limitless growth of the US city and urban landscapes in general.

Weaknesses

The major weakness of the CZM is its lack of applicability beyond the US and for any period before 1900 and after 1950. This is not the fault of the model per se, but rather of the overuse of the model in situations where it is not valid.

Other weaknesses include failure to consider various physical geography factors, not foreseeing the importance of the automobile, ignoring racism, and other factors that blocked minorities from living where they chose and could afford.

Concentric Zone Model Example

Philadelphia provides a classic example of the expansion dynamic inherent to the CZM. Leaving the downtown CBD via Market Street, a trolley line follows Lancaster Avenue northwestward out of the city, paralleling the Main Line of the Pennsylvania Railroad, a major route connecting Philly with points west. Streetcars and later commuter trains allowed people to live in what became known as "streetcar suburbs" in places like Overbrook Park, Ardmore, Haverford, etc.

Even today, it is easy to trace the zones from the CBD outward, as remnants of each can still be seen. The Main Line consists of town after town, each more affluent than the previous one, along the commuter rail and Lancaster Ave/HWY 30 in Montgomery County, Pennsylvania.

Chicago Concentric Zone Model

Chicago served as the original model for Ernest Burgess, as he was a professor at the University of Chicago, which was part of the Chicago Regional Planning Association. This association was attempting to map and model what was happening in this important metropolis in the 1920s.

Burgess identified the place of highest mobility in Chicago as the corner of State and Madison in the Loop, the city's CBD. It had the highest land value. The famous meatpacking zone and other industrial areas formed a ring around the downtown, and beyond that, they were expanding into the slums, which he describes in colorful language as being polluted, dangerous, and impoverished "bad lands," where people from all over the world formed ethnic enclaves: Greeks, Belgians, Chinese, Jews. One such area was where African Americans from Mississippi, part of the Great Migration out of the Jim Crow South, resided.

Then, he described the successive neighborhoods of the working class, middle class, and upper class that were expanding outward in his famous rings and leaving evidence of their presence in old or repurposed homes.