Sociologists studying urbanization trends note three distinct historical stages in the development of cities: preindustrial, industrial, and metropolitan‐megalopolitan stages.
Preindustrial cities
For the vast majority of human history, as far as anyone knows, people roamed about in search of sustenance. While they gathered edible plants, fished, and hunted, our ancestors could never find enough food in one area to sustain themselves for an extended period of time. Consequently, they had to keep moving until they could find another place in which to settle temporarily.
Eventual technological improvements—such as simple tools and information on how to farm and raise animals—allowed people to settle in one place. They built villages, with perhaps only a few hundred people living in each, and, for the following 5,000 years, produced just enough food for themselves—with nothing more in reserve.
About 5,000 years ago, however, humans developed such innovations as irrigation, metallurgy, and animal‐drawn plows. These developments allowed farmers to produce an excess of food beyond their immediate needs. The resulting surplus of food led some people to make their living in other ways: for instance, by making pottery, weaving, and engaging in other nonagricultural activities that they could sell or exchange with others for the surplus food. As a result, people moved off the farms, commerce developed, and cities began to form.
Preindustrial cities—which first arose on fertile lands along rivers in the Middle East, Egypt, and China—were quite small compared to today's cities. Most preindustrial cities housed fewer than 10,000 inhabitants. Others, like Rome, may have contained as many as several hundred thousand people.
Preindustrial cities differed significantly from today's cities. The residential and commercial districts were not as sharply separated as they are today. Most traders and artisans worked at home, although people with the same trades tended to live in the same areas of town. People in cities also segregated themselves from one another according to class, ethnicity, and religion—with little or no chance for social mobility or interaction with other groups.
Industrial cities
Between 1700 and 1900, increasing numbers of people moved into cities, resulting in an urban revolution. For example, in 1700 less than 2 percent of British people lived in cities, but by 1900 the majority of them did so. The United States and other European countries soon attained similar levels of urbanization, driven by the Industrial Revolution.
Industrialization produced the mechanization of agriculture, which, in turn, limited the amount of work available on farms. This lack of employment forced farm laborers to move to cities to find work. This migration of workers from rural to urban areas then gave rise to the industrial city.
The industrial city was larger, more densely populated, and more diverse than its preindustrial counterpart. It contained many people of varying backgrounds, interests, and skills who lived and worked together in a defined amount of space. The industrial city also served as a commercial center, supporting many businesses and factories. The latter attracted large numbers of immigrants from other countries hoping to better themselves by securing stable work and finding a “fresh start.”
Metropolis and megalopolis cities
As larger and larger industrial cities spread outward in the early 1900s, they formed metropolises (large cities that include surrounding suburbs, which are lands outside the city limits, usually with separate governance). While some suburbs become distinct cities in and of themselves, they retain strong geographic, economic, and cultural ties to their “parent” city. Many metropolitan areas house a million or more residents.
The upper and middle classes ultimately brought about the so‐called flight to the suburbs. As economic woes increasingly plagued cities in the latter half of the 1900s, many families decided to move out of their inner‐city neighborhoods and into the suburbs. The ability to afford an automobile also influenced this migration. Beginning in the 1970s, most suburbs were largely “bedroom communities,” which means that suburban residents commuted into the city to work and shop, and then returned to the suburb at night. Commuting presented a downside, but most people felt that escaping “urban ghettoization,” or the tendency for the quality of life in inner cities to decline, was well worth any hassles, given the fact that suburbs tended to offer nicer and larger homes, better schools, less crime, and less pollution than cities provided.
Today, suburbs continue to grow and develop. Many have become economic centers in their own right. Offices, hospitals, and factories coexist with shopping malls, sports complexes, and housing subdivisions. In this way, many suburbs have essentially become small (and, in some cases, not so small) cities. Demographically, suburbs tend to attract “whiter” and more affluent residents than do cities. Yet not all suburbs and suburbanites are alike. Even within a suburb, families of varying ethnic and religious backgrounds exist.
Because of all this growth, many suburbs have developed “urban” problems, such as air and water pollution, traffic congestion, and gangs. To escape these problems, some people have chosen to move to rural areas. Others have chosen to return to and revive their cities by renovating and remodeling buildings and neighborhoods. Such an interest in urban renewal (also called gentrification) has turned some slums into decent areas in which to live, work, and raise a family.
The vast urban complex known as a megalopolis was created as suburbs continued to grow and merge with other suburbs and metropolitan areas. That is, some suburbs and cities have grown so large that they end up merging with other suburbs and cities, forming a virtually continuous region. One example of a megalopolis is the hundreds of miles of almost uninterrupted urbanization from Boston to Washington, D.C. The typical megalopolis consists of literally millions of people.