The nation’s Asian population grew at 3.4% between July 2014 and 2015, with migration responsible for the majority of the growth, government officials said Thursday. There are now 21 million Asians in the United States, with Hawaii as the nation’s only majority Asian state.

Sam Garrow, a Census Department demographer, said Asians have been the fastest-growing race group since about 2000, and the main driving force is international migration. In 2013, China replaced Mexico as the top sending country for immigrants to the United States, officials said.

Other minority groups grew as well. The Hispanic population grew by 2.2% to 56.6 million, and New Mexico had the largest percentage of Hispanics in the country at 48%. The African-American population grew by 1.3% to 46.3 million, with Mississippi holding the nation’s largest percentage at 38.3%. And the American Indian and Alaska native population grew 1.5% to a total of 6.6 million, with Alaska having the largest percent at 19.5%.

California has the largest number of most racial and ethnic groups, with more Hispanics, whites, Asians and American Indians than any other state. New York state has more blacks than any other state, and Hawaii has the largest numeric population of Native Hawaiians than any other state.

The second fastest-growing racial group was those who claim two or more races, government officials said. The number of people who claimed two or more races grew 3.1% to 6.6 million. This group was also the youngest group of all racial or ethnic groups with a median age of 20 years old.

In fact, the most diverse generation is the nation’s youngest. Census figures show that of those born since 2000, nearly half—or 49%—belong to a race or ethnic group other than non-Hispanic white. In contrast, 44.5% of the millennials—born between 1982 and 2000—did not classify themselves as non-Hispanic whites.

Whites Showing Slowest Growth

The nation’s white population is showing the slowest growth.

The census found that the white population, including those who chose white along with another race, grew only 0.5% between 2014 and 2015. There were more than 255 million people who said they were white or white in combination with something else. California had the largest number of these people at 29.8 million, but Vermont had the highest population of those described themselves as white or white along with another race or ethnicity at 96.6%.

The numbers change little for those who say they are white alone. There are 198 million people who say they are white alone, an increase of 0.1%. California once again had the largest population at 14.9 million, but Maine had the largest percentage as its population at 93.6%.

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Sumter County, Florida, Is the Oldest

The oldest place in the United States is Sumter County, Florida, where the majority of the population is at least 65 years old.

Almost 55% of Sumter County has reached retirement age, government figures showed, and the median age in the country was 66.6 years old.

Sumter County also contains one of the fastest-growing areas in the country. The Villages retirement community located northwest of Orlando was the nation’s fastest-growing metro area with a 5.4% increase that raised the population to 114,000 residents. The attraction to areas like The Villages is part of the reason for the increase in population and age, said Jason Devine, assistant division chief for Population Estimates and Projections.

“As the nation’s 65-and-older population grows, other counties with retirement communities like The Villages will get closer to this threshold,” Devine said.

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There was only one other county with a population of at least 1,000 close in age to Sumter County: Catron County, New Mexico. That county had a median age of 60.1 years.

The youngest county in the United States? Lexington County, Virginia, which had a median age of 22.4 years.