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.

Towns

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.

urban area
City lights of Portland, Oregon.

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."

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.

abandon
Verb

to desert or leave entirely.

Noun

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

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.

Noun

number of things of one kind in a given area.

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

resident.

interstate roadway
Noun

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

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.

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.

Noun

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

Noun

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

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.

Noun

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

vegetation
Noun

all the plant life of a specific place.

veteran
Noun

person who has served their country in a military capacity.

Noun

small human settlement usually found in a rural setting.

Noun

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

Noun

environment that has remained essentially undisturbed by human activity.

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.)