The Great Lakes megalopolis consists of a bi-national group of metropolitan areas in North America largely in the Great Lakes region. It extends from the Midwestern United States in the south and west to western Pennsylvania and Western New York in the east and northward through Southern Ontario into southwestern Quebec in Canada. It is the most populated and largest megalopolis in North America.

At its most inclusive, in the United States the region cuts a wide swath from the twin cities of Minneapolis–Saint Paul in Minnesota in the west, south to St. Louis and Louisville, Kentucky, and east to Rochester, New York; in Canada, it continues northeasterly to Quebec City. This broader region had an estimated population of 59,144,461 as of 2011 and is projected to reach a population of about 65 million by 2025. Within this broad region, there is a core area of more continual urban development that includes Chicago, Milwaukee, Grand Rapids, South Bend, Detroit–Windsor, Columbus, Cleveland, Toledo, Pittsburgh, Buffalo, Rochester, Toronto, Ottawa, Montreal, and the metropolitan areas between these.

The region was partially outlined as an emergent megalopolis in the 1961 book Megalopolis: The Urbanized Northeastern Seaboard of the United States by French geographer Jean Gottmann. Gottmann envisaged the development of other megalopolises in the U.S.: from Boston to Washington, D.C., from Chicago to Pittsburgh, and from San Francisco to San Diego.

In 1965, futurist Herman Kahn speculated about the three megalopolises in the year 2000.^[4] In the 1960s and 1970s, urban planner and architect Constantinos Doxiadis wrote books, studies, and reports about the growth potential of the Great Lakes Megalopolis.^[5] Doxiadis envisioned Detroit (on the U.S.-Canada border across from Windsor) as the central urban area in this megalopolis, which he defined as extending "from Milwaukee and Chicago to Detroit, Pittsburgh and Buffalo and into Canada from Windsor to Montreal and Quebec".^[5][6]

In 2005, the Virginia Tech Metropolitan Institute's Beyond Megalopolis, an attempt to update Gottmann's work, outlined a similar "Midwest" megapolitan area as one of ten such areas in the United States (Canada is discussed tangentially).^[7] Over 200 million tons of cargo are shipped annually through the Great Lakes.^[8][9][10] The America 2050 project identified 11 Megaregions of the United States, including the Great Lakes Megalopolis.^[11][A] The Canadian part of the region is also referred to as the Quebec City–Windsor Corridor, and the densest part in Southern Ontario has long been known as the Golden Horseshoe.^{[citation needed]}

There are multiple government jurisdictions throughout the megalopolis. In addition to the federal governments of the United States and Canada, there are multiple U.S. states and two Canadian province jurisdictions, and many county and local governments. Most of the states have joined the provinces in forming the Conference of Great Lakes and St. Lawrence Governors and Premiers to coordinate economic and environmental strategies throughout most of the region.^[12]

The five Great Lakes contain one-fifth of the world's surface fresh water and have a combined shoreline of 10,210 miles (17,017 km). About 200 million tons of cargo are shipped through the Great Lakes each year.^[9][13][14]

The Great Lakes Cruising Coalition supports passenger ship cruises through a joint U.S-Canadian venture to Great Lakes Ports and the Saint Lawrence Seaway.^[15][16]

The Great Lakes Megalopolis is home to many prestigious institutions of higher education. Two founding members of the Association of American Universities (AAU), the University of Chicago in Chicago, Illinois, and the University of Michigan in Ann Arbor, Michigan, are located in the region. The University of Chicago and Northwestern University in the Chicago area are two high-ranking world universities. Other major universities include the University of Toronto in Toronto, Ontario; McGill University in Montreal, Quebec; McMaster University in Hamilton, Ontario; Carnegie Mellon University and University of Pittsburgh in Pittsburgh, Pennsylvania; Case Western Reserve University in Cleveland, Ohio; and the University of Notre Dame in Notre Dame, Indiana.^[17]

The region also contains large multi-campus state university systems such as the University of Illinois System, University of Minnesota System, University of Missouri System, University of Wisconsin System, the University System of Ohio, the State University of New York (SUNY) System, the Indiana University System, and the Purdue University System.

This section does not cite any sources. (August 2020)

The Great Lakes Megalopolis includes the following major inter-urban corridors that are provided with freeway and passenger rail service in both the core and fringe areas of the mega-region. Major waterways for shipping and cruising are also indicated where applicable. Amtrak in the United States and Via Rail in Canada offer rail passenger service, while most Class I freight rail services also connect these points. Major rail shipping services in both Canada and the United States is provided on tracks owned by Canadian National Railway and Canadian Pacific Railway.

This section does not cite any sources. (August 2020)

Several corridors have interstate highways but no comprehensive passenger rail service. These highway routes pass through both core and fringe areas of the Great Lakes megalopolis. The upper Great lakes region has a marine corridor that connects Lakes Superior, Huron, and Michigan. However, this route does not include parallel Amtrak passenger rail or interstate highway service.

• Megalopolis (city type)
• Conference of Great Lakes and St. Lawrence Governors and Premiers
• Megaregions of the United States
• Great Lakes
• Quebec City – Windsor Corridor
• Conurbation
• Combined Statistical Area
• Census Metropolitan Area
• Rust Belt

A. ^ ^a Various sources include Quebec City, Montreal and Ottawa in the Great Lakes Megalopolis, while excluding Minneapolis–Saint Paul, Kansas City, Cincinnati, Indianapolis, Louisville, and Columbus.^[20] All these partial-consensus and non-consensus cities lie at the eastern, western, and southern fringes of the megalopolis.

• Chicago (left) and Milwaukee (center)
• Lakes Erie (right) and Ontario (left)
• Indianapolis (left) to St. Louis (right)
• Cleveland
• Saint Paul
• Fox Cities
• Duluth