Among counties with populations over 100,000, the oldest was Sumter County, Fla., where The Villages retirement community is partially based. The median age there was 68.1. The youngest large county was Utah County, home to the city of Provo, with a median age of 25.7.

Not coincidentally, Utah has some of the highest fertility rates in the nation.

The new census data covers the period up to July 2022.

And while it shows the American population is older than it ever has been, the nation remains younger than its peers in Europe, where the median age is 44, said Kenneth Johnson, a demographer at the University of New Hampshire.

Immigration has historically kept the United States young, as immigrants are generally working-age adults and often have more children than native-born Americans. While immigration has recovered from rock-bottom levels during the pandemic, it has, overall, slowed since 2016.

As the nation ages, it is also becoming more diverse. Between 2021 and 2022, the nation’s Asian population grew by 2.4 percent; the Hispanic population by 1.7 percent; the Black population by 0.9 percent; and the white population by 0.1 percent.