Megalopolis

A megalopolis—also known as a supercity or megaregion—is a cluster of metropolitan areas that function as a single continuous urban zone, linked by shared transportation, economic, ecological, and resource systems. While these regions are integrated enough to make coordinated policy useful, the individual cities within them keep their own distinct identities. The idea has become influential because it shifted thinking about urban growth to a much larger scale.

The word comes from the Greek *megalo-polis*, meaning "big city." It was first used as an aspirational name for the settlement of Megalopolis in Arcadia, southern Greece, founded in the 4th century BC. In modern times, the term took on a geographic meaning by 1832, referring to a very large, densely populated urban complex. In the late 1950s and early 1960s, Jean Gottmann—a political science professor at the University of Paris and a member of the Institute for Advanced Study at Princeton—directed "A Study of Megalopolis" for the Twentieth Century Fund, describing a megalopolis as a "world of ideas." His work applied the term to the urbanized northeastern U.S. seaboard, specifically the corridor from Boston, Massachusetts, to Washington, D.C.

Today, a megalopolis may also be called a megaregion, and various scholars and countries use similar terms for comparable spatial forms. Following Gottmann, a megalopolis involves two or more roughly adjacent metropolitan areas whose shared systems—transport, economy, resources, and ecology—blur the boundaries between population centers. Though some separation remains, perceiving them as a continuous urban area is useful, for instance, to coordinate policy at that expanded scale. In simple terms, a megalopolis is a clustered network of big cities. Gottmann set its population threshold at 25 million, while Doxiadis defined a smaller version at about 10 million. America 2050, a program of the Regional Plan Association, lists 11 megaregions in the United States and Canada. A July 2005 report by Robert E. Lang and Dawn Dhavale of the Metropolitan Institute at Virginia Tech explored U.S. megaregions, and a later 2007 article by Lang and Nelson used 20 "megapolitan" areas grouped into 10 megaregions, based on the original megalopolis model. Modern interlinked ground transportation corridors, like rail and highways, often help develop megalopolises. Using these commuter routes to travel through a megalopolis is informally called megaloping, a term coined by Davide Gadren and Stefan Berteau.

In Brazil, the term *megarregião* has a legal meaning distinct from the English "megaregion," referring instead to mesoregions and microregions. In China, the official term for a megalopolis is *城市群* (chéngshì qún), originally coined by Yao Shimou and literally meaning "city cluster." This is defined as an area where cities are relatively densely distributed in a certain region. An older standard mistranslated it as "agglomeration." In 2019, the National Development and Reform Commission published guidelines distinguishing it from a smaller "metropolitan area" (*都市圈*). In the latest economic and urban planning terminologies, *城市群* is translated as "city cluster," replacing "agglomeration." Chinese megalopolises are now subjects of national government planning.

Because current urban data rely on arbitrary definitions that vary by country, year, or census, making comparisons difficult, an Urban Metric System (UMS) has been conceived to correct this. UMS computes urban area limits and central points and can be applied uniformly to past, present, and future population and job distributions. It is based on vector field calculations assuming that all inhabitants and jobs exert the same attractive force A and repulsive force R. The net force (A - R) from each inhabitant or job is given by [1/(1 + d)] - [1/(β + d/2)], where d is distance and β is the only parameter. UMS distinguishes types of urban areas, including "Megalopolis," each corresponding to a specific β value. It has been applied to some Canadian cases since 2018, but the data in this article still rely on existing national definitions.

In popular culture, the *Judge Dredd* comic book series (1977) features Mega-City One, a huge fictional megalopolis-sized city-state covering much of the eastern United States and part of Canada. Its exact geography varies by writer and artist, but from its first appearance it was linked to New York City's urban sprawl; originally presented as a future New York, it was retconned as the center of Mega-City One in the very next story. *The Architects' Journal* ranked it number one on its list of comic book cities. In William Gibson's *Sprawl* trilogy, "the Sprawl" is a colloquial name for the "Boston-Atlanta Metropolitan Axis" (BAMA), a massive urban sprawl environment and a fictional extension of the real Northeast megalopolis. It imagines a future where virtually the entire U.S. East Coast, from Boston to Atlanta, is a single continuous urban area.