Welcome to the Blueprint of the City!

Have you ever looked at a map of a city and wondered why certain buildings are grouped together? Why are the big skyscrapers usually in the middle, while factories are often near train tracks and big houses are further out? Geographers use urban models to explain these patterns. Think of these models as "blueprints" or simplified maps that help us understand how social and economic forces shape the internal structure of cities. Don't worry if these look like a lot of circles and triangles at first—once you see the logic behind them, they make perfect sense!

The "Why" Behind the Models: Bid-Rent Theory

Before we dive into the specific models, we have to understand Bid-Rent Theory. This is the most important concept for understanding urban land use. In short, it explains that the price of land changes as you move away from the Central Business District (CBD) or "downtown."

  • The Concept: Different users (retailers, manufacturers, and residents) are willing to pay different amounts for land depending on how close it is to the city center.
  • The Rule: Land closest to the CBD is the most expensive because it is the most accessible. As distance from the CBD increases, the price of land drops.
  • The Result: Only big businesses and high-rise offices can afford the land in the center. Factories and houses move further out where land is cheaper.

Quick Formula to remember: \( \text{Price of Land} \downarrow \text{ as Distance from CBD} \uparrow \)


Classic North American Urban Models

Geographers developed three "classic" models based on cities like Chicago. They show how cities grew before everyone had cars and highways.

1. The Concentric-Zone Model (Burgess Model)

Think of this model as a target or a bullseye. It suggests that a city grows outward from a central area in a series of five rings.

  • Zone 1: The CBD. The center where businesses and offices are located.
  • Zone 2: Zone of Transition. An area containing industry and poorer-quality housing.
  • Zone 3: Zone of Independent Workers' Homes. Modest, older houses occupied by stable, working-class families.
  • Zone 4: Zone of Better Residences. Newer, more spacious houses for middle-class families.
  • Zone 5: Commuter Zone. Small villages or "bedroom communities" for people who work in the CBD but choose to live far out.

Memory Trick: Burgess starts with a "B" for Bullseye!

2. The Sector Model (Hoyt Model)

As cities grew, geographers realized they weren't perfect circles. Hoyt argued that cities develop in sectors or wedges, often following transportation routes like railroads or highways.

  • Instead of rings, think of this like a sliced pie.
  • If a rail line is built, factories will grow along that entire "slice" of the city.
  • High-income housing will grow in a wedge as far away from the noisy factories as possible.

3. The Multiple-Nuclei Model (Harris and Ullman Model)

This model moves away from the idea that the CBD is the only center of a city. It suggests that a city has multiple nodes (nuclei) of activity. For example, a university, an airport, and a shopping mall can all act as "mini-centers" that attract different types of land use around them.


The Modern Face of Cities: The Galactic City Model

As the United States became a "car culture" with massive highway systems, the Galactic City Model (also known as the Peripheral Model) emerged. This describes a city where the old CBD is no longer the only focus.

  • The Beltway: The city is surrounded by a highway loop (a "beltway" or "ring road").
  • Edge Cities: Around the highway, new "mini-cities" emerge. These are called edge cities—they have their own offices, malls, and hotels, so people living in the suburbs don't even have to go downtown anymore.
  • Sprawl: This model represents the decentralization of the city.

World Regional Urban Models

Not every city looks like Chicago or Los Angeles! The AP curriculum requires you to know how cities look in other parts of the world. These models reflect the history of colonialism and rapid modern growth.

1. The Latin American City Model

This model combines elements of Latin American culture with the forces of globalization.

  • The Spine and Elite Sector: A narrow "spine" of high-end businesses and amenities leads from the CBD out to an "Elite Residential" sector. This is where the wealthiest people live.
  • Periferico (Zone of Peripheral Squatter Settlements): On the very edge of the city, you find squatter settlements (favelas or barrios). These are areas where very poor residents live in makeshift housing, often lacking basic services like water or electricity.
  • Note the Difference: In the U.S., the poor often live near the center; in Latin America, the poorest often live on the furthest outskirts.

2. The Southeast Asian City Model

The most important feature here is the Port Zone. Because many of these cities grew as colonial trade centers, everything is oriented toward the water.

  • There is no single "CBD," but rather several "commercial zones" (including the Alien Commercial Zone, often dominated by Chinese merchants).
  • Similar to the Latin American model, the outskirts often contain squatter settlements.

3. The Sub-Saharan African City Model

These cities are unique because they often have three CBDs instead of just one:

  1. The Colonial CBD: Built by former European colonizers, usually with a grid street pattern and government buildings.
  2. The Traditional CBD: A center of commerce with more traditional architecture and long-standing businesses.
  3. The Market CBD: An informal, open-air zone where many people buy and sell goods daily.

Quick Review: Key Takeaways

Did you know? Urban models are "idealized," meaning no city fits them perfectly. However, they are vital for AP students to compare how different cultures and eras organize space.

  • Burgess (Concentric): Think Rings/Bullseye (Distance is key).
  • Hoyt (Sector): Think Wedges/Pie Slices (Transportation is key).
  • Multiple-Nuclei: Think Nodes (Cars/Specialization are key).
  • Galactic: Think Highways/Edge Cities (Suburbanization is key).
  • Latin America: Look for the "Spine" and elite sector.
  • Africa: Look for the three different CBDs.
  • SE Asia: Look for the Port Zone.

Common Mistake to Avoid: Don't confuse Bid-Rent Theory with a specific model. Bid-Rent is the economic reason why the models look the way they do (expensive land = high-density buildings in the center).

Note: For more on how these models relate to modern challenges like gentrification or urban sustainability, see the later chapters in Unit 6!