Why New York City keeps getting bigger

New York City skyline

Q: Why is New York City the most populous city in the United States?

A. Because it was America’s most populous city in 1900.

Q. Why was New York City America’s most populous city in 1900?

A. Because it was America’s most populous city in 1800.

History seems to be protecting New York City’s status as the most populous city in the United States. Indeed, Paul Krugman has suggested that accidents of history gave New York City a leg up on others, and that once favored it grew into the metropolis we know today. But New York is not alone. Since 1840, the densest American cities have not only grown substantially, they also represent a larger share of the American population. The same can be said of other world cities, too. They are like snowballs—they’re big and they keep on getting bigger.

But how big cities gained the upper hand is not necessarily an accident, as Krugman’s use of the word might suggest. What has helped them grow so large is actually a specific set of geographic characteristics—location near an ocean or river (or better, both), mild climate, and ready access to natural resources. City founders may not have been working off a checklist, but they knew where to site their settlements to make the most of their surroundings.

It’s no surprise that prosperous cities are often located near large bodies of water. Water is the cheapest way to move goods, and was even more so before the Industrial Revolution. Access to navigable water meant food and raw materials could be easily brought to market and goods manufactured in the city could be cheaply exported. Water facilitated the movement of ideas, too. Both New York City and San Francisco, for example, benefitted from their status as major gateways for immigration. Immigrants were not merely a source of labor—they brought with them a diversity of ideas. Eventually, the importance of water subsided as railroads and interstate highways were built. Yet cities that were founded on coastlines or rivers continued to dominate.

Their size was the secret to their success. One of Krugman’s important early contributions was a model that showed how an already large city could grow to dominate the region. His theory was really nothing new—Johann Heinrich von Thünen described nearly the same thing in 1826—but Krugman translated the concept into today’s mathematical vernacular. Other researchers quickly picked up the thread and dug out real-world evidence of the snowball effect, including one study that looked at population growth in nearly 800 American counties between 1840–1990. It found that not only did the biggest cities grow during that time, they grew at a faster rate than other cities. New York grew more than the rest because it was bigger than the rest.

Today, New York’s fate doesn’t depend on the ocean or the river, but it does owe its status to their confluence. Its geographic past continues to steer its future. I’m tempted to haul out a favorite phrase of mine—ghosts of geography—but these cities aren’t really ghosts. They’re are very much alive. Oceans and rivers may not be as relevant to today’s world cities as they once were, but without them, many cities wouldn’t be as successful. From that perspective, it seems less likely that the founders of New York, London, and Tokyo stumbled on a happy accident and more likely that they had a keen understanding of geography.


Ayuda, M., Collantes, F., & Pinilla, V. (2009). From locational fundamentals to increasing returns: the spatial concentration of population in Spain, 1787–2000 Journal of Geographical Systems, 12 (1), 25-50 DOI: 10.1007/s10109-009-0092-x

Beeson, P. (2001). Population growth in U.S. counties, 1840–1990 Regional Science and Urban Economics, 31 (6), 669-699 DOI: 10.1016/S0166-0462(01)00065-5

Gibson, Campbell. 1998. Population of the 100 largest cities and other urban places in the United States: 1790 to 1990. U.S. Bureau of the Census, Population Division Working Paper No. 27.

Krugman, P. (1991). Increasing Returns and Economic Geography Journal of Political Economy, 99 (3) DOI: 10.1086/261763

Photo by Greg Knapp.

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Ghosts of geography

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