Why This Matters
Urban models are the backbone of how AP Human Geography tests your understanding of cities—and they show up everywhere on the exam. You'll encounter these models in multiple-choice questions asking you to identify land-use patterns, in FRQs requiring you to compare how cities develop differently across regions, and in stimulus-based questions where you'll need to match a city map to its theoretical framework. These aren't just abstract diagrams; they represent real attempts by geographers and economists to explain why cities look the way they do and how social class, transportation, and economic forces shape urban space.
The key concepts these models test include spatial organization, socioeconomic segregation, the role of transportation in development, colonial legacies, and the tension between centralization and decentralization. Don't fall into the trap of just memorizing zone names or model creators—the exam rewards students who understand what each model reveals about urban processes. Ask yourself: What forces shaped this pattern? How does this model differ from others? When you can answer those questions, you're thinking like a geographer.
Classic North American Models: The Foundation
These three models form the core of how geographers first tried to explain urban structure in industrialized Western cities. Each builds on the previous one, addressing its limitations. The key difference among them is how they explain the spatial arrangement of land uses and social classes.
Concentric Zone Model (Burgess Model)
- Developed by Ernest Burgess in 1925—based on Chicago, this was the first systematic attempt to explain urban spatial structure
- Five concentric rings radiate outward from the CBD—zone of transition, working-class homes, better residences, and commuter zone, with wealth increasing with distance from the center
- Assumes uniform land and equal transportation access—this simplification makes it easy to critique but essential for understanding how later models improved upon it
Sector Model (Hoyt Model)
- Homer Hoyt's 1939 model introduced transportation corridors—showing that cities grow in wedge-shaped sectors along rail lines and highways rather than uniform rings
- Similar land uses cluster in sectors radiating from the CBD—industrial zones follow rail lines, while high-income residential areas extend along desirable routes
- Explains why wealthy neighborhoods often form continuous corridors—once established, high-status areas tend to expand outward in the same direction
Multiple Nuclei Model (Harris and Ullman Model)
- Introduced in 1945 to explain decentralization—recognizes that cities develop around multiple centers of activity, not just one CBD
- Different nuclei emerge based on functional specialization—industrial areas cluster near transportation, universities anchor educational districts, and retail centers serve suburban populations
- First model to account for suburban growth and edge development—reflects the automobile age and the rise of specialized districts
Compare: Burgess vs. Hoyt—both assume a single dominant CBD, but Burgess sees growth in rings while Hoyt emphasizes wedges along transportation routes. On an FRQ, use Hoyt when explaining why industrial or wealthy areas form linear patterns rather than circles.
Economic Theories: Why Land Uses Locate Where They Do
These models explain the economic logic behind urban patterns—specifically, how competition for land determines what gets built where. They're less about describing zones and more about explaining the mechanisms that create those zones.
Bid Rent Theory
- Explains land value as a function of distance from the CBD—commercial users pay the highest prices for central locations because accessibility maximizes profit
- Different land users have different bid-rent curves—retail drops off steeply with distance, residential declines gradually, and agriculture can afford only peripheral land
- Directly explains the concentric pattern of land uses—this is the economic engine behind Burgess's zones and appears frequently in exam questions about land-use competition
Central Place Theory
- Walter Christaller's 1933 theory explains settlement hierarchies—larger cities provide higher-order goods (like specialized hospitals), while smaller towns offer lower-order goods (like groceries)
- Threshold and range determine business viability—threshold is the minimum population needed to support a service; range is the maximum distance consumers will travel for it
- Predicts hexagonal market areas in an ideal landscape—while real geography disrupts this pattern, the theory explains why some services cluster in large cities while others are dispersed
Compare: Bid Rent Theory vs. Central Place Theory—bid rent explains land-use patterns within a city, while central place theory explains the distribution and size of cities across a region. Know which scale the question is asking about.
Post-Industrial and Suburban Models
As cities decentralized in the late 20th century, new models emerged to explain polycentric urban forms where suburbs became self-sufficient and the traditional CBD lost dominance.
Urban Realms Model
- Developed in the 1960s to describe metropolitan fragmentation—each "realm" functions as a semi-independent region with its own employment, retail, and residential areas
- Realms are defined by transportation networks and economic activity—the freeway system creates distinct zones that residents rarely leave for daily needs
- Reflects the decline of CBD dominance in American cities—captures how Los Angeles-style sprawl differs fundamentally from older compact cities
Galactic City Model (Edge City Model)
- Joel Garreau's 1990s model identifies suburban employment centers—edge cities have 5+ million square feet of office space and function as urban cores outside the traditional downtown
- Transportation corridors (especially highway interchanges) anchor development—airports, malls, and corporate campuses become new nuclei
- Represents the most decentralized urban form—challenges the assumption that cities need a dominant center at all
Compare: Multiple Nuclei Model vs. Galactic City Model—both show multiple centers, but Harris-Ullman still assumes a dominant CBD with secondary nuclei, while the galactic model shows edge cities that rival or exceed the original downtown. Use galactic for questions about contemporary American suburbanization.
Regional City Models: Global Variations
These models are critical for the exam because they demonstrate how colonial history, cultural factors, and development patterns create urban structures that differ fundamentally from North American models. Expect comparison questions.
Latin American City Model (Griffin-Ford Model)
- Features a commercial spine extending from the CBD—elite residential areas cluster along this corridor, with quality declining outward in concentric zones
- Peripheral squatter settlements (favelas, barrios) ring the outer edge—the inverse of North American cities, where suburbs are wealthier than inner zones
- Reflects colonial planning and rapid rural-to-urban migration—the disamenity zone near the CBD houses marginalized populations in deteriorating housing
Southeast Asian City Model (McGee Model)
- Port zone dominates rather than a traditional CBD—colonial trade patterns shaped these cities around harbors, not central business functions
- Distinct ethnic neighborhoods reflect colonial-era segregation—Chinese commercial districts, European administrative zones, and indigenous residential areas remain visible
- Informal settlements and mixed land use characterize peripheral growth—the Western separation of residential and commercial is less pronounced
African City Model (de Blij Model)
- Features three distinct CBDs—a colonial CBD, a traditional/indigenous market CBD, and sometimes a newer informal commercial zone
- Mining and manufacturing zones create industrial corridors—reflecting resource extraction economies imposed during colonialism
- Informal settlements house the majority of urban residents—rapid urbanization outpaces infrastructure, creating extensive squatter zones
Compare: Latin American vs. African City Models—both show colonial influence and peripheral informal settlements, but the African model's multiple CBDs reflect less integration between colonial and indigenous economies. If an FRQ asks about colonial legacies in urban form, these are your go-to examples.
Quick Reference Table
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| Single CBD with concentric growth | Burgess (Concentric Zone), Bid Rent Theory |
| Transportation shaping urban form | Hoyt (Sector), Urban Realms, Galactic City |
| Multiple centers/decentralization | Harris-Ullman (Multiple Nuclei), Galactic City, Urban Realms |
| Economic competition for land | Bid Rent Theory, Central Place Theory |
| Colonial influence on structure | Latin American, Southeast Asian, African City Models |
| Peripheral poverty/informal settlements | Latin American, Southeast Asian, African City Models |
| Settlement hierarchy and distribution | Central Place Theory |
| Wealth increases with distance from CBD | Burgess Model (North American pattern) |
Self-Check Questions
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Which two models both emphasize transportation corridors as key determinants of urban structure, and how do they differ in scale or focus?
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A city has wealthy residents concentrated along a boulevard extending from downtown to the suburbs, with industrial areas following rail lines in a different direction. Which model best explains this pattern, and why doesn't the Concentric Zone Model fit?
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Compare and contrast the location of informal settlements in the Latin American City Model versus the typical North American pattern shown in Burgess's model. What historical factors explain this difference?
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An FRQ asks you to explain why a specialized cancer treatment hospital locates in a large city rather than a small town. Which theory provides the best framework, and what two key terms should you define in your response?
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How does the African City Model's multiple CBD structure reflect a different colonial experience than the single-spine pattern of the Latin American City Model?