Cities Across the World

By the end of this lesson, students will be able to (per CED LO PSO-6.A):

• Explain the processes that initiate and drive urbanization and suburbanization (per LO PSO-6.A).
• Define megacity (10M+) and metacity (20M+) as distinct spatial outcomes of urbanization (per EK PSO-6.A.3).
• Explain why megacities and metacities are increasingly located in the periphery and semiperiphery (per EK PSO-6.A.3).
• Identify new land-use forms created by suburbanization, sprawl, and decentralization: edge cities, exurbs, and boomburbs (per EK PSO-6.A.4).
• Compare similarities and differences among urban places at different scales and in different regions (per Skill 2.D).

Lesson 6.2 extends LO PSO-6.A with two more EKs. Per EK PSO-6.A.3, "megacities and metacities are distinct spatial outcomes of urbanization increasingly located in countries of the periphery and semiperiphery." Per EK PSO-6.A.4, "processes of suburbanization, sprawl, and decentralization have created new land-use forms — including edge cities, exurbs, and boomburbs — and new challenges." Together they capture the two biggest urban stories of the past half century.

Two simultaneous global trends

At the global scale, two distinct things are happening at once. First, huge cities in low- and middle-income countries keep growing. Second, high-income cities are spreading outward into new suburban forms. Both are CED-named processes; both produce distinct spatial outcomes. The AP exam regularly tests both.

The world's cities come in a range of sizes. Four canonical categories, with the two largest named explicitly in EK PSO-6.A.3.

Why the shift to periphery and semiperiphery?

EK PSO-6.A.3 explicitly notes that megacities and metacities are increasingly located in periphery and semiperiphery countries. The reason combines the six drivers from Lesson 6.1:

• High population growth in the Global South generates more urban residents overall.
• Rural push + urban pull migration concentrates growth in a small number of primary cities (often capital cities).
• Economic development in manufacturing and services creates wage jobs that draw rural migrants.
• Weaker public investment limits spread to multiple smaller cities, so growth concentrates in one or two.

The result: whereas in 1950 most megacities were in the core (Tokyo, New York, London), by 2026 most are in Asia, Latin America, and Africa. Lagos, Karachi, Dhaka, and Kinshasa are all in the top 20 by population in 2026.

Per EK PSO-6.A.4, suburbanization, sprawl, and decentralization have created three specific new land-use forms: edge cities, exurbs, and boomburbs. All three are CED-named and testable.

Suburbanization, sprawl, decentralization

The three processes named in EK PSO-6.A.4 are related but distinct:

• Suburbanization: movement of people and activity from the city center to surrounding, lower-density rings. The broadest term.
• Sprawl: the low-density, car-dependent pattern that often results. Usually a pejorative term reflecting specific built-form characteristics (single-use zoning, strip malls, cul-de-sacs).
• Decentralization: the broader loss of primacy by the historic city center. Includes office decentralization (firms leaving downtown for edge cities), retail decentralization (big-box stores replacing Main Street), and governance decentralization (suburbs forming their own governments).

All three combined produce the new suburban forms EK PSO-6.A.4 names. The result: American urban regions (and increasingly those in the UK, Australia, and parts of the EU and Asia) are polycentric, car-oriented, and low-density relative to traditional city forms.

New challenges that come with them

EK PSO-6.A.4 says these forms produce "new challenges." On the AP exam, you should be able to name at least three: (1) transportation and congestion, (2) environmental impacts (loss of farmland, runoff, emissions), and (3) governance fragmentation across multiple small jurisdictions. Lessons 6.8, 6.10, and 6.11 develop each in depth.

Four cases: two megacity/metacity, two suburban-form.

Bangladesh · Dhaka Metacity

~23M; fastest-growing megacity globally

Dhaka grew from around 2M in 1970 to over 23M by 2024 — among the fastest growth rates of any major city. It is now a metacity per EK PSO-6.A.3. Textile manufacturing draws rural labor; natural increase compounds the migration; weak infrastructure concentrates growth in the capital rather than distributing it. Classic periphery megacity dynamics.

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Japan · Tokyo Metacity (Core Exception)

~37M; world's largest urban agglomeration

Tokyo is the canonical megacity/metacity from the core — proof that EK PSO-6.A.3's "increasingly" is a directional statement, not an absolute one. Since 1950 Tokyo has stayed at the top of global rankings through a combination of high productivity, strong public transit, and restrictive land use. It offers a useful contrast to periphery megacities.

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United States · Phoenix Boomburb Belt

Mesa 510K; Chandler 281K; Gilbert 277K

Phoenix has the nation's densest cluster of boomburbs: Mesa, Chandler, Gilbert, Scottsdale, Glendale, Tempe, and Peoria all exceed 175K residents. All grew after 1970 on cheap land, air conditioning, and the Interstate system. None have historic downtowns in the traditional sense. A laboratory for EK PSO-6.A.4 suburban forms.

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DR Congo · Kinshasa Periphery Megacity

~17M; ~9% annual growth recent decades

Kinshasa exemplifies EK PSO-6.A.3 at an extreme. The city grew from under 500K at independence (1960) to over 17M by 2024, making it larger than Paris. Limited infrastructure investment has concentrated the growth in informal settlements. Now the third-largest francophone city in the world after Paris and Abidjan.

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1. Per EK PSO-6.A.3, megacities and metacities are "increasingly" in the periphery and semiperiphery. What happens to a country when most of its urban growth concentrates in one very large city?
2. Tokyo is a core metacity. Lagos is a periphery megacity. How do the daily lives of residents likely differ? What about governance challenges?
3. Per EK PSO-6.A.4, edge cities, exurbs, and boomburbs represent new US land-use forms. Are similar forms appearing in other core countries (UK, France, Germany, Japan)? Why or why not?
4. Are boomburbs a better or worse way to accommodate population growth than denser urban infill? Defend.
5. Apply Skill 2.D: compare the growth trajectory of Tokyo (1950-2025) with Lagos (1950-2025). What is similar; what differs?

Draft alignment — pending educator review. AP HG codes correspond to the official College Board Course and Exam Description (Effective Fall 2020, V.1). Statements below are paraphrased in CountryReports' own voice; refer to the College Board's published CED for verbatim wording.

AP® and Advanced Placement® are registered trademarks of the College Board. The College Board was not involved in the production of this material and does not endorse it. Standards statements above are paraphrased; codes refer back to the official College Board CED, the NCSS C3 Framework, the Common Core State Standards, and other cited frameworks.