• urban area
    City lights of Portland, Oregon.

    Suburban Sprawl
    Phoenix, Arizona, one of the fastest growing communities in the U.S., has been spreading outward at the rate of an acre an hour.

    White Flight
    One type of suburban migration is connected to the history of racism in the United States. After World War II, many African Americans migrated to cities in the north of the country, such as Philadelphia, New York, and Chicago. Some white residents of these cities then moved to the urban areas surrounding the cities, a suburban migration known as "white flight."

    An urban area is the region surrounding a city. Most inhabitants of urban areas have nonagricultural jobs. Urban areas are very developed, meaning there is a density of human structures such as houses, commercial buildings, roads, bridges, and railways.

    "Urban area" can refer to towns, cities, and suburbs. An urban area includes the city itself, as well as the surrounding areas. Many urban areas are called metropolitan areas, or "greater," as in Greater New York or Greater London.

    When two or more metropolitan areas grow until they combine, the result may be known as a megalopolis. In the United States, the urban area of Boston, Massachusetts, eventually spread as far south as Washington, D.C., creating the megalopolis of BosWash, or the Northeast Corridor.

    Rural areas are the opposite of urban areas. Rural areas, often called "the country," have low population density and large amounts of undeveloped land. Usually, the difference between a rural area and an urban area is clear. But in developed countries with large populations, such as Japan, the difference is becoming less clear. In the United States, settlements with 2,500 inhabitants or more are defined as urban. In Japan, which is far more densely populated than the U.S., only settlements with 30,000 people or more are considered urban.

    Throughout the world, the dominant pattern of migration within countries has been from rural to urban areas. This is partly because improved technology has decreased the need for agricultural workers and partly because cities are seen as offering greater economic opportunities. Most of the worlds people, however, still live in rural areas.


    One type of urban area is a town. A town is generally larger than a village, but smaller than a city. Some geographers further define a town as having 2,500 to 20,000 residents.

    Towns usually have local self-government, and they may grow around specialized economic activities, such as mining or railroading.

    The western part of the United States, for instance, is dotted with "ghost towns." Ghost towns no longer have any human population. They are full of abandoned buildings and roads that have been overtaken by shrubs and natural vegetation.

    Many ghost towns in the western U.S. are the remains of "boom towns," which developed after gold and silver were discovered in the area in the 19th century. Economic activity boomed in these towns, most of it centered on mining. When all the gold and silver was mined, economic activity stopped and people moved away, leaving ghost towns of empty homes and businesses.

    Growth of Suburbs

    Suburbs are smaller urban areas that surround cities. Most suburbs are less densely populated than cities. They serve as the residential area for much of the citys work force. The suburbs are made up of mostly single-family homes, stores, and services.

    Many city residents move to suburbs, a situation known as suburban migration. Homes in suburbs are usually larger than homes in cities, and suburbs usually have more parks and open spaces. Residents may move to escape the traffic, noise, or to enjoy a larger residence.

    Large groups of Americans began to move to suburbs in the late 1800s. The invention of the streetcar made it possible for residents to commute from their homes to their city jobs.

    At the end of World War II, the U.S. government enacted a program that gave home loans to returning war veterans. This created an explosion of single-family homes and increased the growth of suburbs across America.

    The establishment of the Federal-Aid Highway Act of 1956 also contributed to the growth of suburbs and urban areas. The Highway Act created 66,000 kilometers (41,000 miles) of interstate roadway systems. The original plan for the highway system was for the evacuation of large cities in case of a nuclear or military attack. What the Highway Act created instead was suburban sprawl.

    Suburban sprawl continues to be a phenomenon in the U.S. First, outlying areas of a city widen. Slowly, these outlying areas become more crowded, pushing the suburbs farther into rural areas.

    Housing and businesses that serve suburban communities eat up farmland and wilderness. More than 809,000 hectares (2 million acres) of farmland and wilderness are lost to development every year in the U.S.

    Smart Growth

    Recently, experts have tried to curb the spread of suburban sprawl, or at least create urban areas that are developed more purposefully. This is known as "smart growth." City planners create communities that are designed for more walking and less dependency on cars. Some developers recover old communities in downtown urban areas, rather than develop the next piece of farmland or wilderness.

    States such as Oregon are passing laws to prevent unplanned urban sprawl. They have created boundaries around cities that limit the growth of development. Officials have created laws stating that the minimum size of a plot of land is 32 hectares (80 acres). This is to prevent developers from creating suburban communities. An 80-acre plot of land is too costly for a single-family home!

    Other smart-growth communities are creating new types of development. Some have large amounts of undeveloped "green space," organic farms, and lakes.

    Urban areas typically drain the water from rain and snow, which cannot collect in the paved-over ground. Rather than use drainage pipes and ditches, smart-growth communities create wetlands designed to filter storm runoff.

    More city planners are developing urban areas by considering their geography. Engineers build structures that blend with their natural surroundings and use natural resources. White roofs, for example, reflect the suns rays and lower the cost of air conditioning. Homebuilders in urban areas as diverse as Los Angeles, California, and the island communities of Greece create homes and businesses with white plaster or tile roofs for this reason.

    There is also a move toward preserving and maintaining more green areas and planting more trees in urban areas. Landscape designers often consult with city planners to incorporate parks with development.

  • Term Part of Speech Definition Encyclopedic Entry
    abandon Verb

    to desert or leave entirely.

    agriculture Noun

    the art and science of cultivating the land for growing crops (farming) or raising livestock (ranching).

    Encyclopedic Entry: agriculture
    boom town Noun

    urban area that grows very rapidly due to economic opportunity.

    BosWash Noun

    megalopolis between Boston, Massachusetts, and Washington, D.C.

    city Noun

    large settlement with a high population density.

    city planner Noun

    person who plans the physical design and zoning of an urban center.

    commerce Noun

    trade, or the exchange of goods and services.

    commercial Adjective

    having to do with the buying and selling of goods and services.

    commute Verb

    to travel to and from specific places on a regular basis, usually for a specific purpose, such as employment.

    decrease Verb

    to lower.

    density Noun

    number of things of one kind in a given area.

    Encyclopedic Entry: density
    dominant Adjective

    main or most important.

    drainage pipe Noun

    tube that carries wastewater or other material away from a home or business.

    economic opportunity Noun

    situation for a person or group of people to improve their standard of living.

    engineer Noun

    person who plans the building of things, such as structures (construction engineer) or substances (chemical engineer).

    evacuate Verb

    to leave or remove from a dangerous place.

    farmland Noun

    area used for agriculture.

    Federal-Aid Highway Act of 1956 Noun

    law approving construction of 66,000 kilometers (41,000 miles) of interstate roadway systems in the United States.

    geographer Noun

    person who studies places and the relationships between people and their environments.

    ghost town Noun

    urban area that has been abandoned by all residents.

    gold Noun

    valuable chemical element with the symbol Au.

    green space Noun

    area of undeveloped land usually used for recreation.

    hectare Noun

    unit of measure equal to 2.47 acres, or 10,000 square meters.

    incorporate Verb

    to blend or bring together.

    inhabitant Noun


    interstate roadway Noun

    numbered road that stretches between at least two U.S. states. Also called "I" followed by the roadway's number.

    lake Noun

    body of water surrounded by land.

    landscape designer Noun

    person who studies and plans gardens, parks, and other "green spaces."

    megalopolis Noun

    the union of two or more urban areas into a continuous metropolitan area. Also called a conurbation.

    metropolitan area Noun

    region surrounding a central city and has at least 15 percent of its residents working in the central city.

    migration Noun

    movement of a group of people or animals from one place to another.

    mining Noun

    process of extracting ore from the Earth.

    natural resource Noun

    a material that humans take from the natural environment to survive, to satisfy their needs, or to trade with others.

    nuclear attack Noun

    military aggression with explosive devices fueled by the interaction of atomic nuclei.

    organic farm Noun

    land cultivated for crops, livestock, or both, according to guidelines using limited amounts of chemicals.

    outlying area Noun

    land surrounding a specific point.

    phenomenon Noun

    an unusual act or occurrence.

    railroad Noun

    road constructed with metal tracks on which trains travel.

    region Noun

    any area on Earth with one or more common characteristics. Regions are the basic units of geography.

    Encyclopedic Entry: region
    rural area Noun

    regions with low population density and large amounts of undeveloped land. Also called "the country."

    Encyclopedic Entry: rural area
    self-government Noun

    system of control of an area according to that area's residents.

    shrub Noun

    type of plant, smaller than a tree but having woody branches.

    silver Noun

    chemical element with the symbol Ag.

    single-family home Noun

    residential structure that is not attached to another structure. Also called a detached house.

    smart growth Noun

    method of development that serves the community and the environment.

    snow Noun

    precipitation made of ice crystals.

    storm runoff Noun

    rainwater from storms.

    streetcar Noun

    public transportation, usually electric, that runs on rails. Also known as a trolley.

    suburb Noun

    geographic area, mostly residential, just outside the borders of an urban area.

    suburban migration Noun

    movement of people from a city to its suburbs.

    suburban sprawl Noun

    unplanned low-density development surrounding an urban area that often starts as rural land. Also called urban sprawl.

    technology Noun

    the science of using tools and complex machines to make human life easier or more profitable.

    town Noun

    human settlement larger than a village and smaller than a city.

    urban area Noun

    developed, densely populated area where most inhabitants have nonagricultural jobs.

    Encyclopedic Entry: urban area
    vegetation Noun

    all the plant life of a specific place.

    veteran Noun

    person who has served their country in a military capacity.

    village Noun

    small human settlement usually found in a rural setting.

    Encyclopedic Entry: village
    wetland Noun

    area of land covered by shallow water or saturated by water.

    Encyclopedic Entry: wetland
    wilderness Noun

    environment that has remained essentially undisturbed by human activity.

    Encyclopedic Entry: wilderness
    work force Noun

    number of people who are employed or available for employment.

    World War II Noun

    (1939-1945) armed conflict between the Allies (represented by the United States, the United Kingdom, and the Soviet Union) and the Axis (represented by Germany, Italy, and Japan.)