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A Decade of Population Growth and Decline in U.S. Counties

There are a number of factors that determine how much a region’s population changes.

If an area sees a high number of migrants, along with a strong birth rate and low death rate, then its population is bound to increase over time. On the flip side, if more people are leaving the area than coming in, and the region’s birth rate is low, then its population will likely decline.

Which areas in the United States are seeing the most growth, and which places are seeing their populations dwindle?

This map, using data from the U.S. Census Bureau, shows a decade of population movement across U.S. counties, painting a detailed picture of U.S. population growth between 2010 and 2020.

Counties With The Biggest Population Growth from 2010-2020

To calculate population estimates for each county, the U.S. Census Bureau does the following calculations:

 
From 2010 to 2020, Maricopa County in Arizona saw the highest increase in its population estimate. Over a decade, the county gained 753,898 residents. Below are the counties that saw the biggest increases in population:

Phoenix and surrounding areas grew faster than any other major city in the country. The region’s sunny climate and amenities are popular with retirees, but another draw is housing affordability. Families from more expensive markets—California in particular—are moving to the city in droves. This is a trend that spilled over into the pandemic era as more people moved into remote and hybrid work situations.

Texas counties saw a lot of growth as well, with five of the top 10 gainers located in the state of Texas. A big draw for Texas is its relatively affordable housing market. In 2021, average home prices in the state stood at $172,500—$53,310 below the national average.

Counties With The Biggest Population Drops from 2010-2020

On the opposite end of the spectrum, here’s a look at the top 10 counties that saw the biggest declines in their populations over the decade:

The largest drops happened in counties along the Great Lakes, including Cook County (which includes the city of Chicago) and Wayne County (which includes the city of Detroit).

For many of these counties, particularly those in America’s “Rust Belt”, population drops over this period were a continuation of decades-long trends. Wayne County is an extreme example of this trend. From 1970 to 2020, the area lost one-third of its population.

U.S. Population Growth in Percentage Terms (2010-2020)

While the map above is great at showing where the greatest number of Americans migrated, it downplays big changes in counties with smaller populations.

For example, McKenzie County in North Dakota, with a 2020 population of just 15,242, was the fastest-growing U.S. county over the past decade. The county’s 138% increase was driven primarily by the Bakken oil boom in the area. High-growth counties in Texas also grew as new sources of energy were extracted in rural areas.

The nation’s counties are evenly divided between population increase and decline, and clear patterns emerge.

Pandemic Population Changes

More recent population changes reflect longer-term trends. During the COVID-19 pandemic, many of the counties that saw the strongest population increases were located in high-growth states like Florida and Texas.

Below are the 20 counties that grew the most from 2020 to 2021.

Many of these counties are located next to large cities, reflecting a shift to the suburbs and larger living spaces. However, as COVID-19 restrictions ease, and the pandemic housing boom tapers off due to rising interest rates, it remains to be seen whether the suburban shift will continue, or if people begin to migrate back to city centers.

The early 19th century was a time of great change for New York, which had already cemented its status as America’s largest city.

The opening of the Erie Canal helped turn the city into a shipping powerhouse, and there was a building boom on the horizon. Cholera epidemics, fires, and riots swept through the city at various points.

This fascinating interactive map, from Esri, is a snapshot of New York City during the tumultuous time (1836 to be exact), overlaid on the modern-day satellite map.

Getting the Lay of the Land

The base map used above is the stunning “Topographical Map Of The City and County Of New–York, and the adjacent Country”, published by the prodigious mapmaker, Joseph Colton.

For easy viewing, the map’s legend is below:

This map includes all the usual features, such as roads and prominent buildings, but it also has some clever secondary information built in as well. For one, shading indicates ares that were more built-up at the time. There are also a number of visual techniques to indicate topographical features as well. After all, NYC wasn’t as extensive as it is today, and much of the land depicted in the map is still undeveloped.

The full map is well worth exploring as well, as there are a number of beautiful illustrations throughout.

Tool tip: Click the X on the info bar to hide it. (Mobile: Click the map, then the magnifying glass.)

The Big Picture: New York City in 1836

At this point in time, development in Lower Manhattan extended until about 14th Street, where buildings began to give way to open spaces. The city’s grid pattern was beginning to take shape, following the Commissioners’ Plan laid out in 1811. At the time, New York was anticipating massive growth, and the straightforward grid pattern was an efficient way to prepare the city for rapid expansion.

In the 1800s, fire was an ever-present danger for city dwellers. In fact, a major fire tore through Lower Manhattan a year prior to when this map was published.

Points of Interest

There are a number of points worth visiting on this map.

Transit Begins to Take Shape

In the 1830s, New York City’s first railroad line—horse powered for its first few years—connected Prince Street to the Harlem River, accelerating the city’s expansion northward from Lower Manhattan. This route is still recognizable today as the Harlem Line.

Evolving Shorelines

One very obvious difference between the two maps is how much land has been reclaimed along shorelines in the area. Battery Park City, on the west side of downtown, and the Brooklyn Navy Yard are two prominent examples of infill. Randall’s Island, located near the top of Manhattan, is also an interesting place to observe changes in topography. Randall’s Island is actually made up of three islands that were eventually conjoined in the 1960s.

This interactive map is a great place to explore changes to NYC’s shoreline over time.

Taming the Landscape

Midtown Manhattan is worth zooming into for a couple of reasons. First, the outline of Central Park is visible, although the park would officially be approved until almost 20 years later.

As well, this topographical map clearly shows the numerous outcroppings spread across the island. Manhattan was far from flat in the 1800s, and it took a tremendous amount of effort—starting with gunpowder, pickaxes, and horse-drawn carts—to level the land.

Looking at these historical maps is a reminder that the New York City we know today is the product of hundreds of years of human effort, and that cities continue to evolve over time.