"There's some culture shock," said Mark Mather of the Population Reference Bureau, a Washington-based research agency. "But I think there is a momentum building, and it is going to continue."
As of 2006, non-Hispanic whites made up less than half the population in 303 of the nation's 3,141 counties, according to figures the Census Bureau is releasing Thursday. Non-Hispanic whites were a minority in 262 counties in 2000, up from 183 in 1990.
The Census Bureau's report has population estimates by race and ethnicity for every county in the nation. They are the first such estimates since Hurricane Katrina hit the Gulf Coast in 2005, scattering hundreds of thousands of people.
The biggest changes in were in Orleans Parish, La., home to New Orleans. The share of non-Hispanic whites in Orleans Parish grew from 27 percent in 2005 to 34 percent in 2006, while the share of blacks dropped from about 68 percent to 59 percent.
Many of the nation's biggest counties have long had large minority populations. But that diversity is now spreading to the suburbs and beyond, causing resentment in some areas.
Many Latinos say they see it in the debate over illegal immigration.
In northern Virginia, Teresita Jacinto said she feels less welcome today than when she first arrived 30 years ago, when she was one of few Hispanics in the area.
"Not only are we feeling less welcome, we are feeling threatened," said Jacinto, a teacher in Woodbridge, Va., about 20 miles southwest of Washington.
Woodbridge is part of Prince William County, which recently passed a resolution seeking to deny public services to illegal immigrants. Similar measures have been approved or considered in dozens of communities across the nation. In all, state lawmakers have introduced more than 1,400 measures related to immigration this year, the National Conference of State Legislatures says.
Supporters say local laws are necessary because Congress has failed to crack down on the estimated 12 million illegal immigrants in the U.S. But many Hispanics legally in the U.S. say they feel targeted, too.
"I think across the board all of us feel like we're not welcome," said Jacinto, who was born in the U.S. and volunteers for an advocacy group called Mexicans Without Borders.
Prince William County has seen its Hispanic population more than double since 2000, to nearly 70,000 last year. Non-Hispanic whites account for a little more than half the population, down from about two-thirds in 2000.
Greg Letiecq recently helped form a group to fight illegal immigration in northern Virginia, called Help Save Manassas. The group is named for a city surrounded by Prince William County.
"It's not about ethnicity, it's not about race. It's about lawful behavior versus unlawful behavior," Letiecq said.
Still, he complained that many newcomers eschew American culture in favor of their Latino heritage.
"It's the folks who come in and try to maintain the culture of the country they came from," Letiecq said. "They don't seem to embrace the American culture, the English language, the social norms of American culture."
Nationally, the number of minorities topped 100 million for the first time in 2006 -- about a third of the population. By 2050, minorities will account for half of U.S. residents, according to Census Bureau projections.
"I don't think Latinos or any other so-called minority group are seeking to make white people a minority," Jacinto said. "It's just a reality."
By STEPHEN OHLEMACHER--AP