Lorton Station South residents Sherry Feggins, left, and granddaughter Ayanna Burns return home from back-to-school shopping at Potomac Mills. (Tracy A. Woodward/THE WASHINGTON POST)

The Lorton where Chrisdiona Clarke grew up in the 1970s and 1980s bears almost no resemblance to the Lorton where she lives today.

The Fairfax County community, just off Interstate 95, was rural then and — except for the population of a nearby penitentiary — largely white. Clarke remembers awakening to the sound of sirens signaling a prison break. She and her brother, the children of a white mother and a black father, were the only African Americans in their classes at school.

Today, the fields around the prison, which closed in 2001, are filled with upscale houses and apartment buildings. At the newly built town center, many residents gather on summer nights near a courtyard gazebo to hear live jazz before wandering into a restaurant or wine bar.

Non-whites no longer stick out in a crowd. Lorton is one of the most diverse places in the entire country, according to a new study of census data by two sociologists from Pennsylvania State University. The 19,000 residents are roughly a third white and a third black, and there are significant numbers of Asians, Hispanics and multiracial residents.

“I’m in awe of what’s happened,” said Clarke, 37, who left for college and didn’t move back until a year and a half ago, settling in an apartment complex with her husband and daughter. “I love living here.”

What’s happened in Lorton is typical of a demographic sea change that is transforming the Washington area and much of the country. Non-Hispanic whites are a minority in a growing number of metropolitan areas, including Washington. Predominantly white neighborhoods are a relic of the past. New developments that appeal to young families are among the most diverse, drawing Hispanics and Asians who, on average, are much younger than the whites.

Although metropolitan areas are the most diverse, small towns and the countryside are also attracting more minorities. The Penn State researchers found that whites are the predominant group in barely one-third of all places of 1,000 residents or more, compared with two-thirds in 1980.

“Racial and ethnic diversity is no longer a vicarious experience for Americans,” said Barrett A. Lee, one of the study’s authors. “It used to be something that was recognized and debated at the national level. But now even residents of small towns and rural areas are coming face to face with people of different races or ethnicity in their daily lives, not just on the evening news.”

The Washington area stands out for its broad demographic mix. The Penn State researchers ranked the top 25 most-diverse metropolitan areas, and only three metro areas — all in California — had greater diversity than Washington.

The researchers compiled a separate list of the nation’s top 25 most-diverse communities. In addition to Lorton, Germantown and Glenmont in Montgomery County made the list, otherwise dominated by California.

One reason behind Washington’s diversity is that it is what the Penn State study called a “company town,” this one where the government and the military have a large presence.

“When you have communities dominated by institutions that value equal opportunity, you’re going to have a more racially and ethnically diverse population,” Lee said.

Word of mouth among recent immigrants plays a role, too.

“Though the area is a newer gateway than some other communities, now you’ve had several decades of immigrants moving to D.C. and telling their friends and relatives back home it’s a great place to live,” Lee said. “It’s a combination of opportunities and chain migration.”

The pace of change has been rapid, even in older, established neighborhoods.

During the 33 years that Kris Kumaroo has lived in Glenmont, he has watched it morph from a blue-collar, white, working-class community to a place he characterizes as “extremely diverse.”

“We have Sikhs, South Americans, Central Americans,” he said. “I believe we have Eastern Europeans, African Americans. That’s just one street — mine.”

The transition is not always smooth, with cultural traditions and language sometimes forming barriers between neighbors with busy lives and little time to do more than wave from the driveway.

Some longtime residents have to alter their perceptions of what’s acceptable.

“People weren’t used to roosters crowing from 3 a.m. to [6 a.m.,]” said Kumaroo, a former head of the Greater Glenmont Civic Association. “That took some adjusting to.”

Karla Silvestre, manager of Montgomery’s county-run Gilchrist Center for Cultural Diversity, said that schools are important places for neighbors from different backgrounds to mingle and become friends.

“While the kids are playing, the parents talk, and soon they’re organizing a block party and movie night,” she said.

Children are the center of events that bring adults together in Christine Morin’s Lorton neighborhood, where she and her family moved into a new house in 2004.

The neighborhood holds a Fourth of July parade. Halloweens is celebrated with a party at the clubhouse with apple bobs and pumpkin decorations. But the neighborhood also celebrates Diwali, the Hindu festival of lights, during which Indian residents perform traditional dances and serve Indian delicacies. The Chinese New Year is marked with arts and crafts projects for the children and the telling of ancient fables.

“The kids are growing up so differently than I did,” said Morin, who is part Greek and puts together a table explaining Greek traditions on International Night at her children’s elementary school. “We have a lot of Muslim neighbors, so my kids know about Ramadan and Eid. They’re exposed to a lot more different cultures than we were as kids.”

The diversity extends to the townhouses where Sherry Feggins moved in 2005. Many of her neighbors work for the military or the federal government.

“It’s almost like family here,” she said. “When kids are playing, someone will put signs out saying, ‘Kids Playing’ so no cars speed down the street.”

The diversity of her block mirrors Lorton’s statistics, and Feggins ticks off the occupants of the townhouses around her: an Asian family on the corner, then an Indian family, three white families, and another African American like her.

“I’ve never had a neighborhood with this kind of diversity, where you socialize with each other, except on a military installation,” said Feggins, 53, a government budget analyst who married a career Army man.

At the elementary school where Chrisdiona and Asante Clark’s 5-year-old daughter, Ariana, is in first grade, minority children outnumber white children.

“Kids are growing up with a different view of humanity, in which it’s normal to have people of all different colors and languages,” the Gilchrist Center’s Silvestre said. “It’s an amazing experiment in the future, and it’s happening now.”