Despite the growth in some counties, over half (53.6%) of the counties in the United States were smaller in 2019 than they were in 2010. These patterns of growth or decline were largely related to county size, with most small counties losing population this decade and most large counties gaining.



“One interesting trend we have seen this decade is widespread population decline among smaller counties, while larger counties tended to have population growth,” said Dr. Christine Hartley, a demographer in the Census Bureau’s Population Division. “Three out of four counties with a population of less than 10,000 in 2010 had even smaller populations in 2019. At the same time, three out of four counties of 50,000 or more were larger in 2019 compared to 2010.” This pattern among larger counties was particularly evident in the West and South.

Among metropolitan areas, Phoenix-Mesa-Chandler, AZ, with a population of 4,948,203 in 2019, replaced Boston-Cambridge-Newton, MA-NH as the 10th most populous metropolitan area in the country (Table 4). Dallas-Fort Worth-Arlington, TX had the largest numeric gain since 2010, with an increase of 1,206,599 (19.0%) (Table 5).

Of counties with a population of 20,000 or more in 2018 and 2019, Williams County, North Dakota, was the fastest-growing county this decade, increasing by 67.8% (from 22,399 to 37,589) between 2010 and 2019 (Table 3). The rapid growth experienced by Williams County, North Dakota, between 2010 and 2019 was largely due to an 11,233 gain from net domestic migration (movement into the county from elsewhere in the United States). The county also grew between 2010 and 2019 by natural increase (3,400) and net international migration (170).