Edge city is a term that originated in the United States for a concentration of business, shopping, and entertainment outside a traditional downtown or central business district, in what had previously been a suburban residential or rural area. The term was popularized by the 1991 book Edge City: Life on the New Frontier by Joel Garreau, who established its current meaning while working as a reporter for The Washington Post. Garreau argues that the edge city has become the standard form of urban growth worldwide, representing a 20th-century urban form unlike that of the 19th-century central downtown. Other terms for these areas include suburban activity centers, megacenters, and suburban business districts. These districts have now developed in many countries.
In 1991, Garreau established five rules for a place to be considered an edge city:
Has five million or more square feet (465,000 m2) of leasable office space
Has 600,000 square feet (56,000 m2) or more of leasable retail space
Has more jobs than bedrooms
Is perceived by the population as one place
Was nothing like a "city" as recently as 30 years ago. Then it was just bedrooms, if not cow pastures."
Most edge cities develop at or near existing or planned freeway intersections, and are especially likely to develop near major airports. They rarely include heavy industry. They often are not separate legal entities but are governed as part of surrounding counties (this is more often the case in the East than in the Midwest, South, or West). They are numerous—almost 200 in the United States, compared to 45 downtowns of comparable size—and are large geographically because they are built at automobile scale.
Garreau identified three distinct varieties of the edge city phenomenon:
Boomburbs or "boomers" – the most common type, having developed incrementally but rapidly around a shopping mall or highway interchange, for example Tysons, Virginia, near Washington, D.C.
Greenfields – originally master-planned as new towns, generally on the suburban fringe, for example Reston Town Center in Reston, Virginia, near Washington, D.