WASHINGTON D.C.–The 2020 Census showed that the adult (age 18 and older) population group grew 10.1% to 258.3 million people over the decade.

"More than three-quarters, 77.9%, of the U.S. population were age 18 and over," said Andrew Roberts, chief of the Sex and Age Statistics Branch in the Census Bureau's Population Division. "The adult population grew faster than the nation as a whole. By comparison, the population under age 18 was 73.1 million in 2020, a decline of 1.4% from the 2010 Census."

Changes to the adult and under-age-18 populations:

• The District of Columbia had the largest population age 18 and over as a percentage of population at 83.4%. Utah had the largest population under age 18 as a percentage of population at 29.0%.

• Utah also had the fastest-growing adult population at 22.8% growth.

• North Dakota had the fastest-growing population under age 18 at 22.1% growth.

Additional age breakdowns will be available in future 2020 Census data releases scheduled for 2022.

As part of the Census Bureau provided a new data visualization that highlights the adult and under-age-18 populations across the United States down to the county level. More information is available in the America Counts story, U.S. Adult Population Grew Faster Than Nation's Total Population From 2010 to 2020.