The term Megalopolis is derived from Greek and means "very large city." A group of Ancient Greeks actually planned to construct a huge city on the Peloponnese Peninsula. Their plan didn't work out but the small city of Megalopolis was constructed and exists to this day.
Gottmann's Megalopolis (sometimes referred to as BosWash for the northern and southern tips of the area) is a very large functional urban region that "provides the whole of America with so many essential services, of the sort a community used to obtain in its 'downtown' section, that it may well deserve the nickname of 'Main Street of the nation.'" (Gottmann, 8) The Megalopolitan area of BosWash is a governmental center, banking center, media center, academic center, and until recently, an immigration center (a position usurped by Los Angeles in recent years).
Acknowledging that while, "a good deal of the land in the 'twilight areas' between the cities remains green, either still farmed or wooded, matters little to the continuity of Megalopolis," (Gottmann, 42) Gottmann expressed that it was the economic activity and the transportation, commuting, and communication linkages within Megalopolis that mattered most.
Megalopolis has actually been developing over hundreds of years. It initially began as the colonial settlements on the Atlantic seaboard coalesced into villages, cities, and urban areas. Communication between Boston and Washington and the cities in between has always been extensive and transportation routes within Megalopolis are dense and have been in existence for several centuries.
When Gottmann researched Megalopolis in the 1950s, he utilized U.S. Census data from the 1950 Census. The 1950 Census defined many Metropolitan Statistical Areas (MSAs) in Megalopolis and, in fact, MSAs formed an unbroken entity from southern New Hampshire to northern Virginia. Since the 1950 Census, the Census Bureau's designation of individual counties as metropolitan has expanded as has the population of the region.
In 1950, Megalopolis had a population of 32 million, today the metropolitan area includes more than 44 million people, approximately 16% of the entire U.S. population. Four of the seven largest CMSAs (Consolidated Metropolitan Statistical Areas) in the U.S. are part of Megalopolis and are responsible for over 38 million of Megalopolis' population (the four are New York-Northern New Jersey-Long Island, Washington-Baltimore, Philadelphia-Wilmington-Atlantic City, and Boston-Worcester-Lawrence).
Gottmann was optimistic about the fate of Megalopolis and felt that it could work well, not only as a vast urban area, but also as the distinct cities and communities that were parts of the whole. Gottmann recommended that
We must abandon the idea of the city as a tightly settled and organized unit in which people, activities, and riches are crowded into a very small area clearly separated from its nonurban surroundings. Every city in this region spreads out far and wide around its original nucleus; it grows amidst an irregularly colloidal mixture of rural and suburban landscapes; it melts on broad fronts with other mixtures, of somewhat similar though different texture, belonging to the suburban neighborhoods of other cities. (Gottmann, 5)
Furthermore, Gottmann also introduced two developing Megalopoli in the United States - from Chicago and the Great Lakes to Pittsburgh and the Ohio River (ChiPitts) and the California coast from the San Francisco Bay area to San Diego (SanSan). Many urban geographers have studied the concept of Megalopolis in the United States and have applied it internationally. The Tokyo-Nagoya-Osaka Megalopolis in an excellent example of urban coalescence in Japan.
The term Megalopolis has even come to define something much more broadly found than just the northeastern United States. The Oxford Dictionary of Geography defines the term as "any many-centered, multi-city, urban area of more than 10 million inhabitants, generally dominated by low-density settlement and complex networks of economic specialization."
Source: Gottmann, Jean. Megalopolis: The Urbanized Northeastern Seaboard of the United States. New York: The Twentieth Century Fund, 1961.