6.5 The Internal Structure of Cities

TLDR

The internal structure of cities describes how land use, social groups, and economic activity are arranged inside a city. AP Human Geography expects you to explain that structure using the Burgess concentric-zone model, the Hoyt sector model, the Harris and Ullman multiple-nuclei model, the galactic city model, bid-rent theory, and urban models from Latin America, Southeast Asia, and Africa.

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Why This Matters for the AP Human Geography Exam

This topic builds the skill of comparing patterns and trends in maps and spatial data to draw conclusions. On the exam you may need to read a city map or diagram, identify which model fits, and explain why land use is arranged the way it is. You will also use these models to explain spatial patterns, predict likely outcomes when a city grows or transportation changes, and compare cities in different world regions.

Because Unit 6 carries significant weight on the exam, knowing these models lets you respond to multiple-choice questions about urban form and support free-response answers that ask you to apply or compare city structure.

Key Takeaways

• The Burgess concentric-zone model, Hoyt sector model, Harris and Ullman multiple-nuclei model, galactic city model, and bid-rent theory all explain internal city structure in different ways.
• Bid-rent theory explains land value: prices are highest near the central business district (CBD) and drop as you move outward, which shapes who can afford to locate where.
• Many models start from a CBD, but they differ in shape: rings, wedges/sectors, scattered nodes, or a low-density car-based pattern.
• Regional models from Latin America, Southeast Asia, and Africa show how colonial history, informal settlements, and local culture change urban form.
• Each model is a simplification; be ready to explain both what a model shows and what it leaves out.
• Practice matching a labeled diagram to the correct model, since that is a common map-reading task.

The Core Concept: Bid-Rent Theory

Bid-rent theory is the foundation behind most internal city models. It explains how the price people will pay for land changes with distance from the CBD.

• Land near the CBD is the most accessible and has the highest value, so businesses that profit from high foot traffic compete hardest for it.
• As distance from the center increases, land value falls along a bid-rent curve, creating a land value gradient.
• This is why commercial uses tend to cluster centrally, while residential and industrial uses spread outward where land is cheaper.

Understanding this helps you explain why each model arranges land use the way it does.

North American City Models

Burgess Concentric-Zone Model

Developed by sociologist Ernest Burgess in the 1920s, this model shows a city growing outward from the CBD in a series of rings.

• The CBD sits at the center, surrounded by a zone of transition (often older housing and industry mixed together).
• Beyond that are rings of working-class and then higher-income residential areas, with commuters on the outer edge.
• The model uses the idea of invasion and succession, where one group or land use gradually replaces another in a zone.
• Limitation: it oversimplifies real cities and does not fully account for racial and ethnic segregation or modern transportation.

Hoyt Sector Model

Developed by economist Homer Hoyt in 1939, this model arranges land use in wedges or sectors radiating out from the CBD rather than full rings.

• Sectors often follow transportation corridors like rail lines and major roads.
• A type of land use, such as high-income housing, tends to extend outward in the same sector instead of forming a ring.
• Limitation: like Burgess, it simplifies complex social patterns.

Harris and Ullman Multiple-Nuclei Model

Developed by geographer Chauncy Harris and economist Edward Ullman in 1945, this model argues cities grow around several centers, not just one CBD.

• Each nucleus specializes, such as a port, an industrial district, a university, or a shopping area.
• Similar uses cluster together, and incompatible uses (like heavy industry and expensive housing) locate apart.
• This model better fits larger, more complex cities where activity is spread across many nodes.

Galactic City Model (Peripheral Model)

This model describes the decentralized, car-based metropolitan form common in the United States.

• An original CBD remains, but much economic activity shifts to edge cities on the outskirts.
• The term "edge city" comes from journalist Joel Garreau (1991). Edge cities cluster near highway intersections, ring roads, and airports.
• Edge cities mix office, retail, and entertainment, are heavily car-dependent, and can act as regional centers that pull investment away from the old downtown.

Regional Models from Other World Regions

These models show that internal city structure is shaped by colonial history, economic development, and local culture, so it varies between world regions.

Latin American City Model (Griffin-Ford)

• Combines a CBD with a commercial spine and an attached elite residential sector.
• Housing quality often decreases toward the outer edge, where squatter settlements (sometimes called favelas or pueblos jóvenes) develop on the periphery.

Southeast Asian City Model (McGee)

• Often organized around a former colonial port zone rather than a single traditional CBD.
• Includes a mix of commercial districts, ethnic enclaves, and informal market areas.

Sub-Saharan African City Model (De Blij)

• May include several CBD-like areas, such as a colonial CBD, a traditional market CBD, and a transitional business center.
• Surrounding zones often include ethnic neighborhoods and informal settlements.

How to Use This on the AP Human Geography Exam

MCQ

• Be ready to match a labeled diagram or description to the correct model. Look for clues: rings point to Burgess, wedges/sectors point to Hoyt, scattered specialized nodes point to multiple nuclei, and edge cities point to the galactic model.
• Use bid-rent reasoning to answer questions about why certain land uses locate near or far from the CBD.

Free Response

• When asked to explain internal city structure, name a specific model and describe how it arranges land use, not just "the city grows outward."
• For comparison questions, contrast how two models treat the CBD or social groups (for example, rings versus sectors).
• When a prompt involves a city in Latin America, Southeast Asia, or Africa, connect form to causes like colonial history and informal settlements.

Common Trap

• Don't treat every city as having only one center. Real large cities and the multiple-nuclei and galactic models have many activity nodes.

Common Misconceptions

• These models are simplifications, not exact maps. No real city matches one model perfectly.
• Burgess uses rings and Hoyt uses sectors/wedges. Mixing these two up is a frequent error.
• "Edge city" does not mean the original downtown disappears; it means new centers grow on the urban periphery alongside it.
• Bid-rent theory is not just about housing. It explains land value for all uses, which is why businesses outbid others for central locations.
• The regional models are not "worse" versions of North American ones. They reflect different histories and conditions, especially colonialism and informal settlements.

Related AP Human Geography Guides

• 6.1 The Origin and Influences of Urbanization
• 6.2 Cities Across the World
• 6.4 The Size and Distribution of Cities
• 6.3 Cities and Globalization
• 6.6 Density and Land Use
• Unit 6 Overview: Cities & Urban Land-Use