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The Internal Structure
of Cities

Explore the classic urban models that explain how cities are organized: from concentric zones to multiple nuclei, and why land use patterns shape the places we live.

AP Human Geography

What Is Urban Structure?

Urban structure refers to the spatial arrangement of land uses, social groups, and economic activities within a city. Geographers study internal structure to understand why certain neighborhoods are wealthy while others are not, why factories cluster in specific zones, and how transportation networks shape growth.

Essential Vocabulary

CBD
Central Business District: the commercial and financial heart of a city with the highest land values.
Zone of Transition
The area surrounding the CBD characterized by mixed land use, older housing, and industrial activity.
Bid-Rent Theory
The idea that land value decreases with distance from the CBD, influencing who can afford to locate where.

Why Do Urban Models Matter?

Urban models are simplified representations of how cities are organized. They help geographers, planners, and policymakers:

1
Predict growth patterns and plan infrastructure like highways and transit.
2
Explain inequality: why wealthy suburbs and impoverished inner-city zones coexist.
3
Compare cities globally: do Latin American cities follow the same logic as North American ones?

The Concentric Zone Model

5: Commuter Zone 4: Better Residential 3: Working-Class 2: Zone of Transition 1: CBD Burgess, 1925

The Sector Model

Industry Low-Income Middle-Income High-Income CBD Hoyt, 1939

The Multiple Nuclei Model

CBD Industry Low-Income Residential Middle-Income Residential High-Income Suburban Nucleus Airport Harris & Ullman, 1945

Bid-Rent Theory Explained

Land Value Distance from CBD CBD Commercial Industrial Residential

Comparing the Three Models

Concentric Zone Sector Multiple Nuclei
Creator Burgess (1925) Hoyt (1939) Harris & Ullman (1945)
Shape Rings Wedges Irregular clusters
Growth Basis Distance from CBD Transportation routes Multiple activity centers
Best Explains Simple, pre-auto cities Corridor-based growth Modern, polycentric metros
Weakness Oversimplified Ignores multiple centers Hard to generalize

Beyond the Classics: Urban Realms

The Galactic City Model (also called the Urban Realms Model, by James Vance, 1964) describes a metropolitan area where suburban downtowns (edge cities) function independently of the original CBD. Think of a galaxy: each "realm" has its own economic core.

Edge Cities
Self-sufficient suburban centers with offices, retail, and housing (e.g., Tysons Corner, VA).
Beltways
Ring highways connecting suburban realms without passing through the CBD.

The Latin American City Model

Squatter Settlements (Periferico) Zone of Maturity In Situ Accretion CBD Commercial Spine Industrial Griffin-Ford Model, 1980

The African City Model

The de Blij model of the African city reflects colonial legacies. Many African cities have three distinct CBDs reflecting different historical layers:

Colonial CBD
European-planned commercial district with grid streets, often still the administrative center.
Traditional CBD
Pre-colonial market area with informal trade, open-air bazaars, and organic street patterns.
Market Zone
Periodic open-air markets connecting the formal and informal economies at the city's edge.

How to Analyze a City's Structure

1
Locate the CBD. Identify the commercial and financial core: tallest buildings, highest rents, most accessible intersection.
2
Trace transportation corridors. Highways, rail lines, and rivers shape where sectors and nuclei form.
3
Map income patterns. Does wealth increase or decrease with distance from the center? This distinguishes North American from Latin American patterns.
4
Identify secondary centers. Edge cities or industrial parks suggest a multiple nuclei or galactic model.
5
Choose the best-fit model. No real city matches one model perfectly: use the model that explains the most features.

Example: Chicago

Loop Lake Michigan Commuter suburbs Middle-class residential Working-class housing Zone of transition

Example: Los Angeles

Downtown LA Hollywood Irvine Long Beach/Port LAX Area Anaheim

Common Mistakes on the AP Exam

Treating Models as Exact Maps
Urban models are idealizations. No real city perfectly matches any single model. Always note exceptions and overlapping patterns.
Confusing Sector with Zone
The concentric zone model uses rings based on distance. The sector model uses wedges based on transportation corridors. They look very different.
Applying Only North American Models
The AP exam tests global models. In Latin American cities, wealth decreases outward; in many African cities, ethnic divisions matter more than income zones.

Question 1 of 5

In the Concentric Zone Model, which area directly surrounds the CBD?

Question 2 of 5

Homer Hoyt's Sector Model argues that land use patterns are shaped primarily by:

Question 3 of 5

Which urban model best explains the spatial structure of a city like Los Angeles, which has numerous independent suburban employment centers?

Question 4 of 5

In the Latin American City Model, where are the wealthiest residents typically found?

Question 5 of 5

According to bid-rent theory, which type of land use will occupy the area closest to the CBD?