Multiple Nuclei Model

When you travel in the US, do you ever get the idea that you have seen it all before? It's almost eerie: you remember that strip mall with the chain restaurant, nail salon, coffee shop, and two retail stores from the last city you stopped in, but that was three states ago!

You aren't imagining things. US cities are unique, but they also have certain similarities, particularly in their outlying suburbs. It's not just the chain stores but the whole layout of areas that seem to repeat.

Urban geographers are well aware of these similarities, which is why they use models to understand cities and predict how they will grow.

Multiple Nuclei Model Definition

Urban geographers Edward Ullman and Chauncy Harris created the multiple-nuclei model in 1945. It is a model of US cities that improves on two influential but limited models, the Hoyt Sector Model from 1939 and the Burgess Concentric Zone Model of 1925. All three models are associated with the "Chicago School" of urban sociology and are intended to aid urban planners, governments, and the private sector.

Harris and Ullman Multiple Nuclei Model

An abstract colored diagram is usually used to represent the descriptions of the multiple nuclei in this model. The shape of an actual city varies from this abstraction.

Fig. 1 - The Multiple Nuclei Model

Central Business District (CBD)

The model retains this original feature of all US cities, which initially grew up where transportation routes of different types join or cross. The main bus and train stations are here. Because the CBD is the most accessible place to get to for people across the city, it is the best place to be located if you want to sell people things. This influences the fact that the CBD has the highest land values in the city. You will likely see the most expensive shops here.

CBDs have many major retail stores, but they also contain the headquarters of numerous companies, particularly in the financial services industry (banks, insurance firms, etc.). Government buildings are also found here (city hall, federal buildings, and so forth), and some high-rise apartments. There are also restaurants and other service establishments for the large worker population in the CBD during the day.

Wholesale and Light Manufacturing

Attached to the CBD is a separate district for light manufacturing and wholesale warehouses that comprises businesses that cannot pay the high rents of the CBD but need to be close to the hubs of long-distance transportation (rivers, rails, highways, a lake, or sea coast) and accessible to workers (but not shoppers).

Heavy Manufacturing

This district is spatially separated from all other districts except Low-Class Residential because it requires a lot of space and produces a lot of noise, environmental contamination, and other issues that make surrounding land values relatively low. This district just needs to be located along main transportation lines.

Low-Class Residential

The people with the least income reside in this district, the only advantages of which are its proximity to employment in the CBD and manufacturing zones. The many disadvantages include various forms of pollution and the risk of environmental hazards like flooding.

Medium (Middle) Class Residential

This is the largest district in any US city and tends to connect to most other districts; it is on much better land than Low-Class Residential.

High-Class Residential

This district is farther from the city than middle-class neighborhoods and is not connected spatially to the CBD.

Outlying Business District

As US cities grow, new city centers appear. Many but not all of these are minor in size compared to the CBD; they may include districts around universities, hospitals, airports, recreational zones, and so forth. One of the assumptions of the multiple-nuclei model is that like attracts like, and different repels different. Economic activities that bring down land values, such as airports (because of the noise), will repel activities that bring up land values. Thus, universities, which tend to increase surrounding land values, will not be located near airports. Still, they very well may be located next to recreational areas as well as small business districts with shops and restaurants.

Residential Suburb

One of the features of US cities is suburbia. Suburbs emerged in the 20th century with the widespread availability of private automobiles. People left undesirable conditions in cities and moved to outlying areas with more space, cleaner air, lower crime, and so forth. There are many types of residential suburbs for people of all income levels, and most are oriented toward outlying business districts.

Industrial Suburb

The multiple nuclei model recognizes that some suburbs of major cities focus on industrial production that may be cheaper (e.g., lower taxes) or easier (e.g., closer to less-congested transit routes) for businesses to carry out than in the neighboring major city. This is the case with Gary, Indiana, an industrial suburb of Chicago.

Pros of the Multiple Nuclei Model

The multiple nuclei model's main advantage over earlier models is that it is based on the dominance of the private automobile and the road networks that were built in and around cities to maximize the efficiency of commuting and other automobile-focused activities. Little has changed in this respect since the model was developed at the end of World War II.

The road network allowed cities to sprawl so far across the landscape that beltways or ring roads were built to allow traffic to go around cities altogether. In places like Washington, DC, major outlying districts developed along those beltways. In the meantime, CBDs shrank as jobs moved to outlying business districts.

Multiple Nuclei Model Example

The multiple-nuclei model was based on Chicago, Illinois, a city that outgrew its CBD and original industrial district. The first industrial zone in Chicago was adjacent to the CBD along the Chicago River. As Chicago grew to be one of the world's largest cities, another major industrial zone developed along the South Shore of Lake Michigan in the Calumet District, which includes northwestern Indiana industrial suburbs like Gary, Indiana.

Fig. 2 - City Hall and Superior Courthouse, downtown Gary, Indiana, an industrial suburb of Chicago

Los Angeles Multiple Nuclei Model

There is no way to think about Los Angeles without thinking about the automobile. Though the city's roots are centuries old, its explosive modern growth stemming from the film industry but equally from the defense industry, shipping, universities, and so forth is intimately connected to the existence of a vast road network. Los Angeles's famous freeways allow the city proper's almost 4 million residents to blend with Los Angeles County's 9 million and the Greater Los Angeles Metropolitan Area (Los Angeles–Long Beach, CA Combined Statistical Area), with over 18 million people spread across 34,000 square miles.

Greater Los Angeles is so huge that it has developed numerous outlying business districts. Yes, it does have an original CBD (Downtown LA, the Financial District), and an original urban structure organized around it that could have been adequately described by the Concentric Zone model or the Sector Model. But suppose you follow the freeways in any direction. In that case, you come to the outlying districts of Anaheim, Long Beach, Pomona, Chino, Malibu, Simi Valley, Santa Clarita, Santa Ana, Santa Monica, Burbank, and so on. The metro area is divided into the Inland Empire region, Ventura-Oxnard, and Metro LA.

Fig. 3 - Burbank's media district

Mention of southern California's suburbia conjures images of near-endless rows of identical houses snaking across deserts, into canyons, and along the beach. But they contain far more than homes. The suburbs are close to major business districts, not as large as Downtown LA, but still quite important: the downtowns of Pasadena, Glendale, Santa Ana, Riverside, San Bernardino, Burbank, and Long Beach.

Still, though, LA suburbanites don't even need to go to these downtowns to shop and take care of business, as there are numerous edge cities as well, a term referring to clusters of stores, restaurants, clubs, gas stations, and other facilities providing for most of their everyday needs. You know, those confusingly similar locations we mentioned at the beginning of this article!