AP Human Geography — Unit 6
Master urban models, land use patterns, and the forces shaping cities worldwide. Everything you need to ace Unit 6.
Core Ideas
The six big ideas you need to understand before diving into the details.
The process by which an increasing proportion of a population lives in cities. Driven by rural-to-urban migration and natural increase in urban areas.
The commercial and business core of a city. Highest land values, greatest building density, and most accessible by transportation networks.
Theoretical representations of city structure — Concentric Zone, Sector, Multiple Nuclei, and Galactic City models each explain how land use is organized spatially.
The outward growth of cities into surrounding rural areas. Enabled by automobiles, highways, and cheap land; associated with car-dependence and increased commutes.
The reinvestment in and revitalization of older urban neighborhoods, often displacing lower-income residents as property values and rents rise.
A primate city is disproportionately large vs. the next-largest cities. World cities (global cities) are command centers of the global economy: NYC, London, Tokyo.
Spatial Structure
Know each model's author, structure, assumptions, and critiques — these appear frequently on the AP exam.
| Model | Author & Year | Structure | Key Assumption | Limitation |
|---|---|---|---|---|
| Concentric Zone | Burgess, 1925 | Rings expanding outward from CBD; zone of transition, working-class, middle-class, commuter zone | City grows uniformly in all directions on flat terrain | Ignores physical barriers, transportation corridors, and historical patterns |
| Sector (Hoyt) | Hoyt, 1939 | Wedge-shaped sectors radiating from CBD along transportation routes | Land use extends outward along rail/road axes; high-income housing follows desirable corridors | Still assumes a monocentric city; less applicable in polycentric metros |
| Multiple Nuclei | Harris & Ullman, 1945 | Multiple nodes of activity, not just one CBD; specialized districts form around each nucleus | Cities develop around several growth centers (ports, universities, airports) | Hard to predict where nuclei form; doesn't specify spatial arrangement |
| Galactic / Edge City | Harris, 1997 / Garreau | Dispersed low-density development; edge cities around peripheral highway interchanges; CBD declines in dominance | Automobile-dependent sprawl creates suburban employment centers and retail nodes | Primarily describes U.S. cities post-WWII; less applicable globally |
| Latin American City | Griffin & Ford | CBD + commercial spine; elite residential sector along spine; zones of maturity, in situ accretion, and squatter settlements outward | Colonial history, rapid growth, and inequality shape land use differently than in North American cities | Generalizes across very diverse cities; updated by Ford (1996) to add gentrification |
Terminology
Know these terms cold — definitions alone won't cut it, understand how to use them in context.
Rank-Size Rule
The nth-largest city in a country is 1/n the size of the largest city. Indicates a well-integrated national urban system.
Primate City
A city at least twice as large as the next-largest city, dominating the national economy, politics, and culture (e.g., Mexico City, Bangkok).
Blockbusting
Convincing white homeowners to sell cheaply by warning that minorities were moving in, then reselling to minorities at inflated prices.
Redlining
Discriminatory practice of denying mortgages and services to residents of minority neighborhoods, reinforcing segregation.
Edge City
A large suburban node with significant office, retail, and entertainment functions that rivals the traditional CBD (e.g., Tysons Corner, VA).
Urban Renewal
Government-sponsored demolition and redevelopment of "blighted" urban areas, often displacing poor communities (mid-20th century U.S.).
New Urbanism
Urban design movement emphasizing walkable neighborhoods, mixed-use zoning, and transit access as an alternative to auto-dependent sprawl.
Urban Heat Island
Cities are warmer than surrounding rural areas due to impervious surfaces, waste heat, and reduced vegetation.
Squatter Settlements
Informal housing built on land without legal title, common in rapidly growing cities in the Global South (e.g., favelas, shanty towns).
Zoning
Municipal regulations that designate land for specific uses (residential, commercial, industrial) to organize urban space and separate incompatible uses.
Smart Growth
Planning strategy that promotes compact, transit-oriented, walkable, and environmentally sensitive development to counter urban sprawl.
Metacities / Megacities
Megacities have 10M+ residents (e.g., Tokyo, Delhi). Metacities exceed 20M. Growth concentrated in Global South.
Exam Strategy
Unit 6 FRQs often ask you to apply a model, compare cities, or explain a process. Here's how to score every point.
Always name the specific model. Don't just say "a model" — say "the Concentric Zone Model (Burgess)" and then explain its structure. The AP rubric awards points for precise identification.
Link processes to outcomes. If asked about gentrification, explain the cause (reinvestment, rising land values) AND the consequence (displacement of lower-income residents). Causal chains earn full credit.
Use real-world examples. Support every claim with a named city, region, or country. Vague answers like "in developing countries" score lower than "in Lagos, Nigeria" or "São Paulo's favelas."
Distinguish Global North vs. Global South. Urban processes differ dramatically. American cities followed suburbanization; many Global South cities experience rapid in-migration and informal housing. Show you know the difference.
Answer every part of the prompt. Multi-part FRQs (A, B, C) are scored independently. A brilliant answer to part A won't compensate for a missing part C — always attempt every section.
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