Photograph of the region from Richmond, Virginia to New York City, taken from the International Space Station on April 6, 2011 by the Expedition 27 Crew. NASA At night, satellite images show a string of near-constant light along the cities of the U.S. East Coast. Urban growth and sprawl have created a map where Washington blends into Baltimore, and on through Philadelphia, Trenton, New York, Hartford, Providence, and Boston.

The concept of mega-regions dates back to 1957, when the economic geographer Jean Gottmancoined the term “megalopolis” to describe the emerging economic hub that stretched from Boston to D.C. The term came to be applied to a number of regions, including the vast Midwestern megalopolis that extends east from Chicago through Detroit and Cleveland and south to Pittsburgh, which Gottman dubbed “Chi-Pitts,” and many more across the United States and around the world. More than just a collection of cities or one giant city, a mega-region is greater than the sum of its parts.

In earlier research with Timothy Gulden and Charlotta Mellander, we used the satellite images of the globe at night to identify the world’s 40 “mega-regions.” We defined these as a contiguous lighted area with more than one major city or metropolitan region that produced more than $100 billion in economic output.

We found a dozen of these mega-regions in North America – mainly in the United States but spilling over into Canada and Mexico as well. I have written about these mega-regions on Cities before, and I recently completed an updated study of their populations and economies with my colleagues at the Martin Prosperity Institute. I have adapted the results of this newest report for Cities readers below, using more current data to identify the populations and economic size of America’s economic powerhouse regions and see how they would compare to the nations of the world.

The first map, above, shows the populations of North America’s dozen mega-regions. These mega-regions account for 243 metropolitan areas in the U.S. and Canada, including more than 60 percent of all U.S. metros. These dozen regions have a combined population of more than 230 million people, including 215 million from the United States, or 70 percent of the U.S. population. (So-Cal, Cascadia, and Tor-Buff-Chester include parts of Mexico and Canada).

Bos-Wash is the largest, home to 56.5 million people. Denver-Boulder is the smallest, with just shy of 5 million. Still, when compared to the world’s largest economies, Denver-Boulder’s economic output would rank among the 50 largest.

The second map, below, identifies the economic size of these dozen mega-regions and how they compare to nations around the world. The Bos-Wash corridor produces more than Germany, Chi-Pitts more than Brazil, and So-Cal more than all of Mexico. Together, these dozen mega-regions produce more than $13 trillion dollars in economic output, equivalent to three-quarters of America’s total GDP.

A more detailed, region-by-region typology of the country’s mega-regions is below, arranged from largest to smallest by population.

Bos-Wash stretches from Boston through New York, Philadelphia and Baltimore to Washington, D.C., a total of 500 miles. It is home to 18 percent of the U.S. population – 56.5 million people. The region generates $3.75 trillion in economic output, meaning that, if Bos-Wash were a separate country, it would be the fourth largest economy in the world, behind only the U.S., China, and Japan and ahead of Germany.

stretches from Boston through New York, Philadelphia and Baltimore to Washington, D.C., a total of 500 miles. It is home to 18 percent of the U.S. population – 56.5 million people. The region generates $3.75 trillion in economic output, meaning that, if Bos-Wash were a separate country, it would be the fourth largest economy in the world, behind only the U.S., China, and Japan and ahead of Germany. Chi-Pitts extends north and west from Pittsburgh through Cleveland, Detroit, Indianapolis, Chicago, and Minneapolis, taking in more than 50 metros in all. Home to 41.8 million individuals, this mega-region generates $2.3 trillion in output. Its economy is just a bit smaller than the United Kingdom’s, about the same size as Brazil’s, and bigger than all of Russia’s – equivalent to the world’s seventh largest nation.

extends north and west from Pittsburgh through Cleveland, Detroit, Indianapolis, Chicago, and Minneapolis, taking in more than 50 metros in all. Home to 41.8 million individuals, this mega-region generates $2.3 trillion in output. Its economy is just a bit smaller than the United Kingdom’s, about the same size as Brazil’s, and bigger than all of Russia’s – equivalent to the world’s seventh largest nation. Char-lanta, which is home to 22 million people, takes in 45 metros, including Atlanta, Georgia; Raleigh, North Carolina; and Birmingham, Alabama. With more than a trillion in economic output, its economy is bigger that South Korea’s, placing it among the world’s fifteen largest economies.

which is home to 22 million people, takes in 45 metros, including Atlanta, Georgia; Raleigh, North Carolina; and Birmingham, Alabama. With more than a trillion in economic output, its economy is bigger that South Korea’s, placing it among the world’s fifteen largest economies. So-Cal runs from L.A. through San Diego and spills into Tijuana, Mexico, accounting for 21.8 million people and more than one trillion in economic output. Even excluding its Mexican component, its economy is bigger than all of Mexico’s and just a bit smaller than Spain’s, also putting it among the world’s fifteen largest economies.

runs from L.A. through San Diego and spills into Tijuana, Mexico, accounting for 21.8 million people and more than one trillion in economic output. Even excluding its Mexican component, its economy is bigger than all of Mexico’s and just a bit smaller than Spain’s, also putting it among the world’s fifteen largest economies. So-Flo includes Miami, Orlando and Tampa and is home to 15 million people. It produces more than $750 billion in economic output, making it about the same size as the Netherlands or Turkey, and would therefore rank among the world’s twenty largest economies.

includes Miami, Orlando and Tampa and is home to 15 million people. It produces more than $750 billion in economic output, making it about the same size as the Netherlands or Turkey, and would therefore rank among the world’s twenty largest economies. Nor-Cal includes San Francisco, San Jose, Oakland and 14 other metros surrounding San Francisco Bay. It has a population of 13 million people and produces more than $900 billion in output, roughly the same as Indonesia, and more than Turkey. This also lands it among the world’s twenty largest economies.

includes San Francisco, San Jose, Oakland and 14 other metros surrounding San Francisco Bay. It has a population of 13 million people and produces more than $900 billion in output, roughly the same as Indonesia, and more than Turkey. This also lands it among the world’s twenty largest economies. Tor-Buff-Chester stretches north from Buffalo and Rochester, taking in Toronto, Ottawa and Montreal in Canada. It has an estimated population of more than 16 million (several smaller Canadian metros are not included in this tally). It generates output of nearly $600 billion, more than Sweden, placing it among the world’s 25 largest economies.

stretches north from Buffalo and Rochester, taking in Toronto, Ottawa and Montreal in Canada. It has an estimated population of more than 16 million (several smaller Canadian metros are not included in this tally). It generates output of nearly $600 billion, more than Sweden, placing it among the world’s 25 largest economies. Dal-Austin encompasses Dallas, Austin, and San Antonio, Texas. Its population is just under 12 million. It produces more than $700 billion in economic output, more than Sweden or oil-rich Saudi Arabia. It also would rank among the 25 biggest economies in the world.

encompasses Dallas, Austin, and San Antonio, Texas. Its population is just under 12 million. It produces more than $700 billion in economic output, more than Sweden or oil-rich Saudi Arabia. It also would rank among the 25 biggest economies in the world. Hou-Orleans , the great energy-producing belt that stretches from Houston through Mobile, Alabama to New Orleans, is home to more than 10 million people. It produces more than $750 billion in economic output, about the same as the Netherlands, placing it among the world’s 25 largest economies. (Some researchers have suggested combining Houston, Dallas-Ft. Worth and Austin into a single “Texas Triangle.” This mega would include 20 million people, and its $1.5 trillion economy would be comparable to Australia’s and just a bit smaller than India’s or Canada’s.)

, the great energy-producing belt that stretches from Houston through Mobile, Alabama to New Orleans, is home to more than 10 million people. It produces more than $750 billion in economic output, about the same as the Netherlands, placing it among the world’s 25 largest economies. (Some researchers have suggested combining Houston, Dallas-Ft. Worth and Austin into a single “Texas Triangle.” This mega would include 20 million people, and its $1.5 trillion economy would be comparable to Australia’s and just a bit smaller than India’s or Canada’s.) The Cascadia mega-region, which stretches up from Portland, Oregon through Seattle and into Vancouver, Canada, is home to nearly 10 million people. It generates economic output of about $600 billion, comparable to Switzerland, also placing it among the world’s top 25 nations.

mega-region, which stretches up from Portland, Oregon through Seattle and into Vancouver, Canada, is home to nearly 10 million people. It generates economic output of about $600 billion, comparable to Switzerland, also placing it among the world’s top 25 nations. Phoenix-Tucson is home to more than 5 million people and generates economic output of more than $250 billion, just slightly less than Hong Kong. This makes it one of the fifty largest economies in the world.

is home to more than 5 million people and generates economic output of more than $250 billion, just slightly less than Hong Kong. This makes it one of the fifty largest economies in the world. Denver-Boulder has 4.2 million people and $256 billion in economic output, more than Finland, Greece or Ireland. If it were a nation, it would also rank among the world’s 50 largest economies.

Population data are from the U.S. Census Bureau American Community Survey and from Statistics Canada. The data on economic output for both U.S. metros and nations are from the most recent Metro Economies Report from the U.S. Conference of Mayors (the metro data is predictive for 2014, while the national GDP data covers the most recent year available, 2012); Canadian data are from the Montreal Chamber of Commerce. Karen King and Zara Matheson of the Martin Prosperity Institute compiled the data and Matheson created the maps.