When you are staring at the Empire State Building, you know you are in a city. When you are standing in an Iowa cornfield, you have no doubt that you are in the country. Geographers help explain why urban and rural settlements are different. Chapter 12 and this chapter are both concerned with urban geography, but at different scales. The previous chapter examined the distribution of urban settlements at national and global scales. This chapter looks at where people and activities are distributed within urban areas.

Cities & Geography

Historically, urban settlements were very small and compact. As these settlements have rapidly grown, however, definitions have been created to characterize their different parts: the metropolitan area, the central city, and the urban area.

Central City

A central city (or simply city) is an urban settlement that has been legally incorporated into an independent, self-governing unit known as a municipality. Virtually all countries have a local government system that recognizes cities as legal entities with fixed boundaries. A city has locally elected officials, the ability to raise taxes, and responsibility for providing essential services. The boundaries of the city define the geographic area within which the local government has legal authority.

In the United States, population has been declining in most central cities in the North and East. For example, population has declined since 1950 by more than one-half in the central cities of Buffalo, Cleveland, Detroit, Pittsburgh, and St. Louis. In contrast, people are migrating into cities in large numbers in the U.S. South and West, as well as in many developing countries.

Metropolitan Area

Studies of urban settlements in the United States are usually based on the metropolitan statistical area (MSA), which measures the functional area of an urban settlement. The MSA was created by the U.S. Office of Management and Budget (OMB), using U.S. Census Bureau data, to reflect the extensive area of economic and cultural influence of settlements (Figure 13-1). An MSA encompasses the following:

• An urbanized area with a population of at least 50,000. (Urbanized area is defined below.)

• The county within which the city is located. In New England, towns are sometimes used instead of counties.

• Adjacent counties with a high population density and a large percentage of residents working in the central city’s county (specifically, a county with a density of 25 persons per square mile and at least 50 percent working in the central city’s county).

Definitions of Urban Settlements

MSAs are widely used to define urban settlements because many statistics are published for counties, the basic building block for MSAs in most states. OMB designated 392 MSAs (including 8 in Puerto Rico) as of 2018, encompassing 86 percent of the U.S. population.

OMB has also designated smaller urban areas as micropolitan statistical areas (μSAs). A μSA includes an urbanized area of between 10,000 and 50,000 inhabitants, the county in which it is located, and adjacent counties tied to the city. The United States had 546 micropolitan statistical areas as of 2018, for the most part found around southern and western communities previously considered rural in character. About 9 percent of Americans live in micropolitan statistical areas.

OMB combines MSAs and μSAs in several ways:

• A core-based statistical area (CBSA) is any one MSA or μSA (938 as of 2018, including the 392 MSAs and the 546 μSAs).

• A combined statistical area (CSA) is two or more contiguous CBSAs tied together by commuting patterns (175 as of 2018).

Eleven of the largest MSAs are subdivided into metropolitan divisions. For example, the Seattle-Tacoma-Bellevue MSA is divided into the Seattle-Bellevue-Kent and the Tacoma-Lakewood metropolitan divisions.

Urban Area

An urban area consists of a central city and its surrounding built-up suburbs. The U.S. census recognizes two types of urban areas:

• An urbanized area is an urban area with at least 50,000 inhabitants.

• An urban cluster is an urban area with between 2,500 and 50,000 inhabitants.

The census identified 486 urbanized areas and 3,087 urban clusters in the United States as of 2010. Approximately 70 percent of the U.S. population lived in one of the 486 urbanized areas, including about 30 percent in central cities and 40 percent in surrounding jurisdictions. Approximately 10 percent of the U.S. population lived in one of the 3,087 urban clusters.

Overlapping Metropolitan Areas

A megalopolis is a collection of adjacent or overlapping metropolitan areas that merge into a continuous urban region. The word is derived from the Greek meaning “great city.” Geographer Jean Gottmann applied the term Megalopolis (with a capital M) specifically to a continuous urban complex in the northeastern United States that extends from north of Boston to south of Washington, D.C.

Megalopolis

Also known as the Boswash corridor, Megalopolis extends more than 700 kilometers (440 miles) between north of Boston and south of Washington. Megalopolis contains one-fourth of the U.S. population on only 2 percent of the country’s total land area. The red lines show boundaries between MSAs and μSAs, and the white lines show boundaries between counties within a single area.

Other urban complexes exist in the United States, including the southern Great Lakes between Milwaukee and Pittsburgh, and southern California, between Los Angeles and Tijuana. Among important examples in other developed regions are the German Ruhr (including the cities of Dortmund, Düsseldorf, and Essen), Randstad in the Netherlands (including the cities of Amsterdam, The Hague, and Rotterdam), and Japan’s Tokaido (including the cities of Tokyo and Yokohama).

Within Megalopolis, the downtown areas of individual cities such as Baltimore, New York, and Philadelphia retain distinctive identities, and the urban areas are visibly separated from each other by open space used as parks, military bases, and farms. But at the periphery of the urban areas, the boundaries overlap.

Pause & Reflect 13.1.1

Do you live inside or outside a central city? An urban area? A metropolitan area?