SAN MARINO, Calif. » Beneath the palm trees that line Huntington Drive, named for the railroad magnate who founded this Southern California city, hang signs to honor families who have helped sponsor the centennial celebration here this year. There are names like Dryden, Crowley and Telleen, families that have lived here for generations. But there are newer names as well: Sun, Koo and Shi.

A generation ago, whites made up roughly two-thirds of the population in this rarefied Los Angeles suburb, where most of the homes are worth well over $1 million. But Asians now make up over half of the population in San Marino, which has long attracted some of the region’s wealthiest families and was once home to the Western headquarters of the John Birch Society.

The transformation illustrates a drastic shift in California immigration trends over the last decade, one that can easily be seen all over the area: More than twice as many immigrants to the nation’s most populous state now come from Asia than from Latin America.

And the change here is just one example of the ways immigration is remaking America, with the political, economic and cultural ramifications playing out in a variety of ways. The number of Latinos has more than doubled in many Southern states, including Alabama, Georgia and North Carolina, creating new tensions. Asian populations are booming in New Jersey, and Latino immigrants are reviving small towns in the Midwest.

Much of the current immigration debate in Congress has focused on Hispanics, and California has for decades been viewed as the focal point of that migration. But in cities in the San Gabriel Valley — as well as in Orange County and in Silicon Valley in Northern California — Asian immigrants have become a dominant cultural force in places that were once largely white or Hispanic.

"We are really looking at a different era here," said Hans Johnson, a demographer at the Public Policy Institute of California who has studied census data. "There are astounding changes in working-class towns and old, established, wealthy cities. It is not confined to one place."

Asians have become a majority in more than half a dozen cities in the San Gabriel Valley in the last decade, creating a region of Asian-dominated suburbs that stretches for nearly 30 miles east of Los Angeles. In the shopping centers, Chinese-language characters are on nearly every storefront, visible from the freeways that cut through the area.

Monterey Park, a middle-class city that began attracting Asian immigrants more than a generation ago, is still widely seen as the area’s center and retail hub. But as Asians have continued to arrive in Southern California, they have moved into some of the most exclusive cities in Los Angeles County, making up more than 60 percent of the population in San Gabriel and Walnut, along the county’s eastern edge.

Many of the immigrants come here from China and Taiwan, where they were part of a highly educated and affluent population. They have eagerly bought property in places like San Marino, where the median income is nearly double that of Beverly Hills and is home to one of the highest-performing school districts in the state. The local library now offers story time in Mandarin.

But the wealth is not uniform, and there are pockets of poverty in several of the area’s working-class suburbs, particularly in Vietnamese and Filipino communities.

"This is kind of ground zero for a new immigrant America," said Daniel Ichinose, a demographer at the Asian Pacific American Legal Center. "You have people speaking Mandarin and Vietnamese and Spanish all living together and facing many common challenges."

The children of the immigrants who began transforming the area a generation ago are beginning to come of age, becoming cheerleaders for the region, running for political office and creating businesses that cater to a distinctly American-born audience.

There are countless stores that display signs in Mandarin, sell restaurant supplies and Chinese herbs, or advertise acupuncture or brokerage services. But perhaps the most common storefront is the boba tea shop, where young patrons spend hours drinking cold milk tea with jellylike tapioca balls. Nearly every one of the region’s hundreds of strip malls boasts a cafe — or even two — offering a dizzying number of variations on the sweet drink.

Andrew and David Fung, who grew up in Seattle, were surprised to see the pervasiveness of Chinese and Taiwanese culture in the San Gabriel Valley.

After moving to the area a couple of years ago to try to break into the entertainment industry, the Fung brothers created several hip-hop videos celebrating what they termed the "boba life," to embrace the area where, as their lyrics explain, "kids drink more milk tea than liquor." The videos became so wildly popular on the Internet that local leaders began showing them in official meetings.

"People here think it’s normal, hanging out to drink boba all day long, but this culture doesn’t exist everywhere, and we’re trying to tell them to embrace it, to own it," said David Fung, 26. "We’ve got to teach ourselves to be proud of who we are and tell others about it."

The Fung brothers have helped create a local ethnic pride that would have been unimaginable a generation ago, said Oliver Wang, a professor of sociology at California State University, Long Beach, who grew up in San Marino in the 1980s and returned to the area three years ago. The area could become central to Asian-American identity in the region in the way East Los Angeles is to Latinos or South Los Angeles is to African-Americans, he said.

"It wasn’t cool to be Chinese or cool to be Asian," he said. "The idea that the San Gabriel Valley could be the locus of some kind of cultural movement or identity is fascinating. They are asserting cultural capital to create Asian-American identity that wasn’t there before, and one that is homegrown, not imported from Taiwan or Hong Kong."

But the growth has not come without some backlash. While there is rarely overt tension in the area these days, there is a history of clashes over English-only ordinances, and some people still speak in hushed tones about Chinese immigrants taking over the region.

More recently, there have been renewed complaints of "maternity tourism," a cottage industry that brings Chinese women here to give birth so that their children can have American citizenship. Residents, including Asian immigrants, have complained to local officials about large houses that host dozens of pregnant women at a time.

Jay Chen, 35, a member of the Hacienda Heights school board in the San Gabriel Valley, recalled a 2010 controversy over a plan to create a Chinese-language class at a local middle school. Last year, when Chen challenged a longtime Republican congressman, Ed Royce, to represent a newly drawn district, he received a handful of messages using anti-Asian slurs.

"There’s still this conservative element that said teaching Chinese meant you were teaching communism," said Chen, who lost the race. "Meanwhile, people are fighting to get into our district so their children — of whatever ethnicity — can take these classes."

Food often draws outsiders to the region, which is packed with mom-and-pop restaurants where a feast can cost less than $20.

Last summer, Jonny Hwang, 32, a son of Taiwanese immigrants, created the 626 Night Market. (Its name is play on the region’s area code.) More than 15,000 people clogged the streets to get in. "It surprised everyone," Hwang said. "All of the sudden we had a community and something that even other people wanted."

© 2013 The New York Times Company