A stroll along devon Avenue, a commercial artery on Chicago's north side, is like taking a culinary tour of the world.
Restaurants cater to almost any taste - from borscht to baklava. There is tandoori chicken for Pakistanis, falafel on Israeli menus, and blini for Russian devotees. The street is a striking example of the American melting pot.
But a drive northwest of Las Vegas tells a different story. Five years ago, there were 1,000 homes in the area. Today, there are 57,000. The influx is transforming the salmon sands of the desert into a middle-class development - one overwhelmingly white.
Welcome to America's new demographic magnets with strange two-way powers. A handful of urban centers are drawing record numbers of immigrants. But they're also pushing away native residents to other regions of the country that are older, more middle class, and far less diverse. Some demographers warn that this new divide will make it harder for the US to assimilate its latest wave of immigrants.
The political and economic implications are enormous. The last time so many newcomers piled onto US shores - nearly a century ago - native-born citizens and immigrants lived in different neighborhoods but rubbed shoulders on the way to work. No longer. If current trends continue, they'll have to wave from airplane windows.
By 2025, according to one estimate, 12 states could have populations less than 60 percent white, while another 12 would have white populations in excess of 85 percent.
"The US is not becoming a single melting pot the way we thought of it at the turn of the century," says William Frey, senior fellow at the Milken Institute, a think tank in Santa Monica, Calif. Instead, it's stirring multiple melting pots in a few large metropolises, while much of the rest of the country diversifies much less slowly or not at all.
The great divide cuts across traditional boundaries and draws new ones. Suburbs are starting to look more like cities. So many immigrants are flooding some areas that they could change the definition of what it means to be an American.
"The notion is that those [immigrants] get assimilated into the American mainstream," says William Clark, a Los Angeles geographer. But "if you've got 4 [million] to 5 million Hispanics in L.A. County, assimilation to what?... What's the American mainstream?"
In some places, it's hard to tell. Consider: A record 26 million immigrants already live in the US and some 800,000 to 900,000 newcomers arrive legally each year (another 400,000 come illegally). That's nearly 10 percent of the population - not quite as high as the early 1900s but double the percentage of 1970.
Typically, the newcomers are younger, poorer, and less well-educated than the native-born population (although a liberal sprinkling are more highly educated). They're also much more likely to have children.
The influx of immigrants plus the children they bear has accounted for nearly 60 percent of the nation's population growth since 1990. That's a sharp break from the early part of the century when fertility rates among native-born Americans were also high.
Moreover, today's immigrants are more concentrated than ever, says Mark Krikorian, executive director of the Center for Immigration Studies, a Washington think tank. The top four gateway states - California, New York, Florida, and Texas - have a 20 percent greater share of the nation's immigrant population than the top four states did in past years. Some two-thirds of those who arrived in the US between 1985 and 1997 settled in just 10 metropolitan areas, says Mr. Frey.
While new Americans are flowing to these gateway metropolises, native-born Americans are fleeing. Eight of the 10 largest magnet cities for the foreign born lost native-born populations. And the leave-takers aren't moving to the suburbs, they're leaving the region entirely.
Although it exists, fear of immigrants isn't firing the new regionalism. It's the promise of better jobs, lower living costs, and less congestion in places such as Phoenix and Denver.
These places are usually also less ethnically diverse and more middle class.
Take Las Vegas, the No. 2 destination for native-born Americans. "They drive in with little or no connection to Las Vegas, open the newspaper, and find six pages of jobs for skilled or unskilled workers," says Joseph Dias, a sociologist at the University of Nevada, Las Vegas.
But it's not just white flight, says Mr. Krikorian. "Some of it is black flight." African-Americans are moving back to the Southeast and to Texas. Atlanta, the No. 1 destination for nonimmigrants, saw the largest increase of blacks - and whites - of all metropolitan areas between 1990 and 1997.
Immigrants are also breaking the mold. Whereas previous waves settled the inner city, many of today's newcomers bypass it for the job-rich suburbs. In Los Angeles, many Asians head directly to the San Gabriel Valley. In Chicago, most Indian immigrants choose the suburbs over the city because a majority are higher-educated professionals and can afford to buy homes, says Rob Paral, a Chicago research consultant on immigration issues.
As a result, the suburbs of the melting pots are beginning to look a lot more like their central cities rather than the rest of America. For its own special reasons, Los Angeles looks like the prototype.
"We don't have a city-versus-suburb distinction," says Dowell Myers, professor of urban planning and demography at the University of Southern California. "It goes back to the original geography. [Unlike Eastern cities], Los Angeles didn't grow up around a port, a railhead, or a river. It grew up on a flat plain - a series of dispersed settlements from the beginning."
So many immigrants are going to California they're diversifying almost the entire state. More than one-quarter of California's population is foreign-born. Ten of its cities are so diverse that no ethnic group makes up a majority. Demographers now talk of the "Latinization" of rural California.
To be sure, other parts of the country are also diversifying. Meat-packing plants in Iowa and chicken farms in Georgia are attracting an influx of immigrants to some rural communities. "There is more diversity in more places than we expect," says Larry Long, a demographer at the US Census Bureau.
But in wide swaths of the Midwest and Southeast, diversification is happening much more slowly, if at all, Frey argues. The glacial pace of change in these regions will widen the great divide and carries with it enormous political and economic implications.
"Both parties will have to deal with it," Frey says. "You have a lot of socially liberal folks who used to live in the suburbs of New York City or L.A., who are moving to Middle Atlantic states."
In the melting-pot cities, meanwhile, African-Americans may have to share some of their newfound political power as other ethnic minorities grow. "As groups get more diverse, it becomes less of an issue of 'us versus them' and more a matter of building coalitions," says Phil Nyden, director of the Center for Urban Research at Loyola University in Chicago.
Economically, immigrants are helping companies fill low-paying jobs. But they also help hold down wage rates and work jobs that offer little future. "Certainly working as a maid in a hotel doesn't have the same kind of pay and long-term prospects as working in the steel mill 30 or 40 years ago," Mr. Nyden says.
The influx also strains municipal budgets. Because most immigrants are poor, they require more city services and are less able to pay for them through taxes. Their children need to be taught English in the schools, draining more resources.
There's little consensus whether the rise in immigration helps or hurts America. "On the one hand, immigrants are assimilating into American society more rapidly than they did in the past," says Krikorian, a critic of the rapid influx of newcomers. "On the other hand, American society itself has changed fundamentally.... We are importing people and teaching them that these are the various castes and tribes that they need to belong to, and we're going to subsidize that difference and celebrate that difference and reject the notion of a common identity."
Demographer Reynolds Farley is more optimistic. Just as past waves of foreigners worked and succeeded in the US, "it's hard to imagine that that process will not repeat itself," says Mr. Farley, who works at the Russell Sage Foundation, a social-science research organization in New York. "There's an immigration momentum that's going to continue."