The United States is a nation of immigrants, but immigration can cause stress, as newcomers and established residents adapt to each other. From Los Angeles, Mike O'Sullivan looks at immigration in California, the leading destination for many U.S. immigrants, who are forced by necessity to learn to live with others.

California cities are a magnet for immigrants, who settle, interact, and create a new identity in their adopted homeland. William Frey, a population expert at the Brookings Institution in Washington DC, says Los Angeles is a classic "melting pot," much as New York City was in the 19th century.

"It is getting numerically the most immigrants, also in terms of people coming in with different backgrounds and different cultures, different languages, certainly non-English speakers. It is an area that is continually churning, continually intermixing, and I don't think there is any other part of the United States today, or maybe even historically, that has the magnitude and the turbulence of the demographic change that is occurring in Los Angeles today," says William Frey.

Los Angeles is home to Armenians, Africans, Thais, Iranians and many others. Some, like Koreans and Filipinos, form the largest ethnic enclaves outside their native countries.

Immigrants often settle in communities where others from their country already live. In San Francisco's Chinatown, new immigrants from China and Taiwan find their traditional foods and social institutions, and can function easily in their native dialects.

Liang Liang, from Shanghai, China, runs a small import shop with his uncle in downtown Los Angeles. He says most of his customers are Korean, Filipino, or Mexican.  They communicate in sometimes-broken English, or other languages.

One-third of Californians are Hispanic, and some trace their roots here back many generations, to the time when the state was part of Spanish-colonial Mexico. But others are recent immigrants, including several million who are thought to be in the United States illegally.

Ira Mehlman of the Federation for American Immigration Reform says illegal immigration should be stopped.  He would also like to see legal immigration reduced drastically. He says there are hundreds of millions of people who would like to move here, but the United States cannot accept them all.

"You know, it took until about 1830 for the human population of the planet to reach its first billion. Now we have six-and-a-half billion. We grow at a rate of about a billion people every decade. You simply cannot apply the same rules under those circumstances that you were able to apply when this was a relatively sparsely populated planet and this was a sparsely populated continent," says Ira Mehlman.

There have been efforts in the past to restrict immigration, some fearing the loss of jobs and others fearing the introduction of alien cultures. In the 19th and early 20th centuries, much of the anti-immigrant sentiment in the United States was based in California.

Archivist Susan Goldstein of the San Francisco Public Library says popular music and pamphlets warned of the threat of immigrants from China and Japan.

"We also have signs that were made by the labor movement exhorting people to come out to demonstrations to protest against the Chinese and later the Japanese in San Francisco.  We even have one thing, a cigar box, and on the label is "made by white men only," and that is a label that you would see a lot at the time to show that it was not made by Asian labor," says Susan Goldstein.

There may be tensions among people of different religions, ethnicity and race, says Robin Toma of the Los Angeles County Commission on Human Relations.  The agency was created following ethnic violence in Los Angeles in the 1940s.  The commission conducts education campaigns in schools and community centers, as it works to combat hate crimes and defuse tensions.

'We know that conflict is inherent.  The question is, how do you deal with it?  Do you bury it and ignore it and let it affect things behind the scenes and the way people feel, or does it get brought out, aired, and then everybody agrees, you put it behind you as best you can," says Robin Toma.

Many communities offer English classes or educational programs to help immigrants adapt, even as ethnic communities work to keep alive their distinctive traditions.

Mark Baldassare of the of the Public Policy Institute of California says opinion polls show most Californians consider illegal immigration a drain on the state's resources, but have positive views of immigrants in general.

Mark Baldassare

“I think California is the melting pot, in a way that Ellis Island was for European immigrants, California is for immigrants from Asia and Latin America, as well as Europe, and the Middle East increasingly as well. And in California, this very diverse melting pot has led to an entry point for people into the U.S. in which they feel the U.S. is a diverse and welcoming society," says Mark Baldassare.

Harry Pachon of the Tomas Rivera Policy Institute says immigration is changing the culture and complexion of the United States. It is happening, more than anywhere, in California, where whites are no longer in the majority.

"It's a melting pot and it's the new America of the 21st century. White is going to get a little bit darker in the latter decades of the 21st century. That bothers some people, and other people think it's a very healthy sign for American culture," says Harry Pachon.