11.1: Defining Cities

Though it seems simple enough, distinguishing cities from rural areas is not always that easy. Countries around the world have generated a plethora of definitions of “city” based on a variety of urban characteristics. Part of the reason stems from the fact that defining what constitutes urban is somewhat arbitrary. Cities are also hard to define because they look and function quite differently in different parts of the world.

Complicating matters are the great variety of terms we use to label a group of people living together. Hamlets, for example, are very small, rural communities. Villages are slightly larger, but exactly what makes a village distinct from a hamlet is arbitrary. Towns are larger than villages. Cities are larger than towns. Then there are words like metropolis and megalopolis to denote huge cities. Some states in the United States have legal definitions for these terms, but most do not. The US Census Bureau creates the only consistent definition of “city”, and it uses the terms “rural” and “urban” to distinguish cities from non-city regions. This definition has been updated several times since the 1800s, most radically in recent years as the power of GIS has allowed the geographers working for the US Census Bureau to measure multiple factors of urbanity simultaneously.

For decades, the US Census recognized an area as “urban” if it had incorporated itself as a city or a town. Incorporation indicates that a group of residents successfully filed a town charter with their local state government, giving them the right to govern themselves within a specific space within the state. Until recently, the US Census Bureau classified almost any incorporated area with at least 2,500 people as “urban”.

However, there were problems with those simple definitions. Some cities, even a few with large populations, remained unincorporated, and thus failed to meet the incorporation test for inclusion as a city. For example, Honolulu, Hawaii and Arlington, Virginia are not incorporated and therefore were labeled “census designated places” by the government, rather than “cities”. Conversely, some incorporated areas had very few people. This can happen when a city loses population, or when the boundaries of a city extend far beyond the populated core of the city. You may have witnessed this as you are driving on a highway, and you see a sign indicating “City Limits”, but houses, shops, factories and other indicators of urban life are absent yet for many miles. Jacksonville, Florida is the classic example of this problem. Jacksonville annexed so much territory that its city limits extend far into the adjacent countryside making it the largest city in land area in the United States (874.3 square miles!). California City, California is similar. It’s the third-largest city in California in terms of acreage but has only about 15,000 people (Look at it on Google Maps).

Figure 11-2: Jacksonville, FL. Jacksonville's city limits include all the area in the light tan - most of Duval County. According to the US Census, only the area in the dark tan in the center is actually "urban".

Therefore, the Census Bureau created a complex set of criteria capable of evaluating a variety of conditions that define any location as urban or rural. A key criterion now used by the Census is a minimum population density of 1,000 people per square mile, regardless of the incorporation status of the location. Additionally, any places that include non-residential urban land uses are included in the definition of “urban”. Therefore, areas with factories, businesses or a large airport, even those that contain few residences are still counted as part of a city. The Census uses a measure of surface imperviousness to help make such a decision. This means that even a parking lot may factor into the classification of a place as“urban”. Finally, the census classifies locations that are near an urban region if it has a population density of at least 500 persons per square mile. That way, small breaks in the continuity of built-up areas do not result in the creation of multiple urban areas. Instead,single contiguous regions are created using that technique. So, people living in a suburb within five miles of the border of a larger city, are counted by the Census as residents of the nearby city.

Census Designations

Because the terms, “village”, “town” and,“city” are problematic, the US Census Bureau devised another set of more precise terms to help us distinguish urban areas based on population and the manner in which people commute to work.

At the top of the urban hierarchy are Combined Statistical Areas (CSA); massive urban conglomerations that function as a single huge city. The most populous CSA in the United States is anchored by New York City (23.5 million people) and includes smaller cities and towns in northern New Jersey, eastern Pennsylvania, and southern Connecticut. In California, Los Angeles anchors a CSA of 18.35 million people that includes everyone living in Ventura, Orange, Los Angeles, San Bernardino, and Riverside Counties. The City of Los Angeles itself contains only 3.8 million, of which 1.5 million are in the San Fernando Valley.

A step down from the CSA is what the Census Bureau calls Metropolitan Statistical Areas (MSA), which like the CSA includes multiple cities or counties, but with even closer economic ties as measured by the commuting pattern of workers. Again New York City anchors the most populous of these, followed by Los Angeles, Chicago, and Dallas-Fort Worth. Los Angeles’ CSA is officially known as “Los Angeles-Long Beach-Santa Ana, California” and it includes only Los Angeles and Orange County. To the north is the “Oxnard-Thousand Oaks-Ventura” MSA, which includes just the cities in Ventura County.

The Census Bureau classifies smaller cities with between 10,000 and 50,000 people as “urban clusters”. When such a city is the focal point of commuting among residents living in the surrounding region, the census designates the “city” as a Micropolitan Statistical Area (μSA – the μ is the Greek letter “mu”). Though the “anchor” city must be less than 50,000, large semi-rural or suburban populations may live within easy commuting distance. Torrington, Connecticut, for example, anchors a μSA that has close to 200,000 people, though less than 35,000 live in Torrington itself.

People who live in on a farm, in the woods, or in towns with fewer than 10,000 people may still be part of a larger μSA, MSA or CSA, and so be technically part of some urban system in the United States. There are many thousands living in these small towns or in areas beyond easy commuting distance of a city. The Census Bureau considers these sorts of places rural. In California, only a handful of regions are not “urban” in some fashion. Two such towns in California are Lee Vining and Bridgeport, two touristy villages in Mono County well-known to many who have driven through while vacationing on the Eastern Sierra Nevada.