Based on the 2020 U.S. census data, America grew more slowly in the past decade than at any time in over half a century. Over the 10 years since 2010, U.S. population growth barely topped 7%. An aging population and decisions by many Americans to delay marriage contributed to this most modest increase to 331,449,281.
Population growth varied substantially among America’s slightly more than 3,000 counties. In Alexander County, Illinois, the population dropped 36.4% to 5,240. According to The Wall Street Journal, much of the loss was in Cairo, once a bustling river port that “has suffered for decades from the decline of shipping, coal mining, government and manufacturing jobs.”
At the far end of the spectrum, the population in one county more than doubled from 2010 to 2020. The number of McKenzie County, North Dakota, residents grew by 131.2% to 14,704. The county sits on the far western border of the state, where it meets Montana. Its county seat, Watford City, posted an even faster growth, from 1,744 residents in 2010 to 7,944 last year.
The county’s population growth is largely the result of the huge fracking boom in the Bakken oil field. Oil produced by pressurized liquids forced into rock formations helped the United States get a measure of energy independence. This production peaked in late 2019. High-paying jobs in the industry drew tens of thousands of people to the area.
The median household income in McKenzie County is unusually high. At $77,845, it sits about $10,000 above the comparable national number. This is every state’s best county to live in.
The second fastest-growing county in America over the period is also in North Dakota. Williams County posted a population growth rate of 82.8% to 40,950. It is immediately north of McKenzie County, and the reason for its growth is the same. The median household income in Williams County is even higher, at $87,161.
Will the growth of these counties continue over the next decade? Almost certainly not. While the fracking boom has not ended entirely, the industry has taken a downturn, driven by a drop in the price of crude. These are the states with the best and worst economies.
Click here to see the 20 fastest-growing counties in America
20. Rockwall County, Texas
> 2020 population: 107,819
> 2010 population: 78,337
> Pct. Change in population: 37.6%
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19. Sumter County, Florida
> 2020 population: 129,752
> 2010 population: 93,420
> Pct. Change in population: 38.9%
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18. Stark County, North Dakota
> 2020 population: 33,646
> 2010 population: 24,199
> Pct. Change in population: 39.0%
17. Nantucket County, Massachusetts
> 2020 population: 14,255
> 2010 population: 10,172
> Pct. Change in population: 40.1%
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16. Fort Bend County, Texas
> 2020 population: 822,779
> 2010 population: 585,375
> Pct. Change in population: 40.6%
15. Kaufman County, Texas
> 2020 population: 145,310
> 2010 population: 103,350
> Pct. Change in population: 40.6%
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14. Madison County, Idaho
> 2020 population: 52,913
> 2010 population: 37,536
> Pct. Change in population: 41.0%
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13. Forsyth County, Georgia
> 2020 population: 251,283
> 2010 population: 175,511
> Pct. Change in population: 43.2%
12. St. Johns County, Florida
> 2020 population: 273,425
> 2010 population: 190,039
> Pct. Change in population: 43.9%
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11. Williamson County, Texas
> 2020 population: 609,017
> 2010 population: 422,679
> Pct. Change in population: 44.1%
10. Osceola County, Florida
> 2020 population: 388,656
> 2010 population: 268,685
> Pct. Change in population: 44.7%
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9. Lincoln County, South Dakota
> 2020 population: 65,161
> 2010 population: 44,828
> Pct. Change in population: 45.4%
8. Trousdale County, Tennessee
> 2020 population: 11,615
> 2010 population: 7,870
> Pct. Change in population: 47.6%
7. Wasatch County, Utah
> 2020 population: 34,788
> 2010 population: 23,530
> Pct. Change in population: 47.8%
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6. Bryan County, Georgia
> 2020 population: 44,738
> 2010 population: 30,233
> Pct. Change in population: 48.0%
5. Comal County, Texas
> 2020 population: 161,501
> 2010 population: 108,472
> Pct. Change in population: 48.9%
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4. Dallas County, Iowa
> 2020 population: 99,678
> 2010 population: 66,135
> Pct. Change in population: 50.7%
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3. Hays County, Texas
> 2020 population: 241,067
> 2010 population: 157,107
> Pct. Change in population: 53.4%
2. Williams County, North Dakota
> 2020 population: 40,950
> 2010 population: 22,398
> Pct. Change in population: 82.8%
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1. McKenzie County, North Dakota
> 2020 population: 14,704
> 2010 population: 6,360
> Pct. Change in population: 131.2%
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