The share of the white population fell to 57.8 percent in 2020 from 63.7 percent a decade prior, the data show.

In California, Hispanics became the largest racial or ethnic group, growing to 39.4 percent from 37.6 percent over the previous decade, while the white population dipped to 34.7 percent from 40.1 percent.

There were also significant increases among people who identify as multiracial, Hispanic, and Asian, driving much of the population growth throughout the decade. People who identify as multiracial increased by 276 percent, to 33.8 million in 2020 from 9 million in 2010.

The largest gains were among Hispanics, who now make up 18.7 percent of the population, the data show.

Overall, the U.S. population grew by just 7.4 percent during the previous decade, which is the second slowest growth on record, according to the census data. The population grew to 331.4 million in 2020 from roughly 308.7 million in 2010. Only the decade spanning the 1930s—when the Great Depression occurred—had a slower growth rate.

The opioid epidemic and lower birth rates among white millennials accelerated the decline in the white population, the Brookings Institution's William Frey said in a Washington Post interview.