Washington’s population was limited for much of its history to whites and blacks, who went about their business in a culture defined by racial segregation.

The whites, many of whom traced their roots to England and Scotland, dominated the nation’s capital. In 1900, a century after the city’s founding, they made up about two-thirds of the residents. They controlled the federal government, made the decisions in city halls and local courthouses, occupied the prime real estate, had most of the money, dominated the social register, and put statues of white generals in the parks.

After World War II, aided by a boom in affordable housing and expanding highways, they settled by the tens of thousands in the new suburbs of Maryland and Virginia served by shopping malls and mostly white schools.

Against this backdrop, Washington’s coloration came from blacks. They made up 31 percent of area residents in 1900. While many were poor and working-class and all struggled against bigotry, these African-Americans built a sizable middle-class community with thriving institutions, including Dunbar High School, Howard University, many churches, and the U Street shopping and entertainment corridor. With opportunities created by the civil-rights movement of the 1960s, they elected their own to the DC mayor’s office and transformed Prince George’s County into one of the country’s centers of black affluence.

What Washington did not have was the rich mix of European immigrants who had landed in New York City, Boston, Philadelphia, Baltimore, and other cities. Washington was not a major port for oceangoing passenger ships and had no heavy industry demanding immigrant labor, so it was bypassed by the big waves of newcomers. While a third of New York City residents were foreign-born in 1900, the number in Washington was just 7 percent. So it was New York that became famous for neighborhoods filled with Italian and Jewish immigrants and for its Irish-dominated political machine.

Washington’s layout was conceived by a Frenchman, Pierre Charles L’Enfant, and it did accumulate a few tinges of ethnicity as it grew. Italians were imported to carve statuary on the Capitol, and Irish helped build the Chesapeake & Ohio Canal. A German immigrant, Christian Heurich, became the city’s leading brewer, and there were enough Jewish immigrants by 1876 to establish Adas Israel as their first synagogue. The main outpost of non-Europeans was Chinatown, but it was tiny in comparison with New York’s or San Francisco’s.

International influences in Washington, especially after World War II, came outside the normal channels of immigration and derived from its status as a center of a world power. Dozens of newly independent nations established embassies. Well-educated professionals came here from across the globe to staff the World Bank, the International Monetary Fund, and the Organization of American States. And universities attracted many foreign students. In 1957, Muslim diplomats built a mosque on Massachusetts Avenue in DC, the first on this side of the Atlantic.

The region’s historical norm—mostly native-born whites and blacks—was reflected in the 1970 census, which showed just under 5 percent of the population as foreign-born. But this was changing. The taxi drivers were likely to be newly arrived from Africa, India, Pakistan, and many other countries. Affluent white professionals with children hired nannies and housekeepers from Central and South America, who began to displace an older generation of African-American domestics.

Many mom-and-pop shops, once owned by Jews, were bought by Korean immigrants, who also moved into dry cleaning. Adams Morgan came to be known as a community with lots of Latinos. Adventurous diners sought out places like Mama Ayesha’s Calvert Cafe (Middle Eastern), Mamma Desta (Ethiopian), the Taj Mahal (Indian), and the Omega (Cuban).

Then there was the arrival of Vietnamese refugees after the fall of Saigon in 1975. Vietnamese restaurants were opened in Georgetown, and a strip of Vietnamese restaurants and shops in Clarendon became known as Little Saigon. A South Vietnamese police chief seen in an iconic photo shooting a captured Vietcong in the head in Saigon quietly opened a restaurant in Northern Virginia. All of which gave credence to a dark joke: “We may have lost the war, but at least we got some new restaurants.”

Those indicators of growing immigration now seem old news. The Washington region has become one of the country’s largest gateways for immigrants—behind Los Angeles, New York City, Chicago, and Miami. The proportion of foreign-born here, just one in 22 in 1970, is now about one in five. It’s likely, when figuring in undocumented aliens who may not have been counted in the census, that this area now has more than a million immigrants.

For Washington, this is a demographic change of historic dimension, pushing the city even more rapidly than the rest of the country into a world more complicated than shades of black and white. The area’s white population is now 54 percent of the total, compared with 46 percent minority (26 percent black, 10 percent Hispanic, 8 percent Asian, and 2 percent other races).

With immigration expected to grow, a tipping point when whites will be outnumbered by other races seems inevitable. William Frey, a demographer at the Brookings Institution, projects it could come around 2020 and that three decades from now, in 2036, the numbers will be 45 percent white, 27 percent black, 14 percent Hispanic, 13 percent Asian, and 1 percent other races. The region’s core (DC, Arlington, Alexandria, Fairfax County, Fairfax City, Falls Church, Montgomery, Prince George’s) already has passed this tipping point and is now 49 percent white, 30 black, 12 percent Hispanic, and 9 percent Asian.

While Washington was once mocked for its ethnic blandness, recent immigrants have introduced a stunning level of variety. A study by Audrey Singer of Brookings found that about 85 percent of newcomers here during the 1990s came from Asia, Latin America, Africa, and the Caribbean—a reversal of the situation between 1930 and 1960, when most were from Canada and Europe. Beyond that are other dimensions of difference—young and old, illiterates and PhDs, the affluent and the poor, those fluent in English and those who can barely speak a word.

While many immigrants have jobs as dishwashers, janitors, convenience-store clerks, or construction laborers, others are highly skilled scientists, engineers, and doctors. And while many struggle to pay their rent and have no health insurance or car, others have the wealth to afford homes in the more affluent Zip codes and send their children to top colleges.

A few immigrants have achieved a measure of fame, including Kojo Nnamdi, the WAMU talk-show host, from Guyana; Natwar Gandhi, DC’s chief financial officer, from India; John Darwish, founder of the auto dealership Darcars, from Iran; and Dr. Elias A. Zerhouni, director of the National Institutes of Health, from Algeria. Foreign-born athletes are no longer uncommon, from former Georgetown basketball stars Patrick Ewing (Jamaica) and Dikembe Mutombo (Congo) to Nationals outfielder Alfonso Soriano (Dominican Republic) and DC United’s Jaime Moreno (Bolivia).

The influx of immigrants has reshaped many neighborhoods, especially in suburbs inside the Beltway. The region now has 30 Zip codes where more than 30 percent of residents are foreign-born, nine of those above 40 percent. There’s a Little Mexico in the Riverdale section of Prince George’s, a New Chinatown in Montgomery County, a Little Ethiopia in DC, a Salvadoran-dominated Little Chirilagua in Alexandria, and a Korean commercial center in Annandale. The old Birchmere country-music nightclub in Arlandria is now a Salvadoran-Mexican restaurant, and the Crossroads, a Bladensburg nightclub where guitarist Roy Buchanan was once the main draw, is now a leading nightspot for West Indians.

Public schools were the first to feel the powerful effects of immigration. Montgomery County has 40 schools with more than 30 percent Latinos, and Fairfax County has 35. Arlington County’s elementary schools have children from 128 countries, and officials converted an old Safeway into a new school to accommodate some of them.

Hospitals are affected too, mostly as poor immigrants without health insurance show up in emergency rooms, accounting for much of the traffic at such places as Holy Cross Hospital in Silver Spring.

Several suburban strip malls, including some that were getting seedy, have been revived by immigrant entrepreneurship. In a mall on the west edge of Alexandria, a big-box store that once was a Shoppers Food Warehouse is now a Korean-owned Grand Mart International Food store, and around it are Chinese, Vietnamese, Korean, and Peruvian restaurants.

Downtown Wheaton, once as white as any postwar suburb, is now an ethnic stew of restaurants and stores catering to various ethnic groups. The old Shalom Strictly Kosher market has been joined by a Filipino restaurant, a Brazilian clothing boutique, a Salvadoran restaurant, and an immigration-law office. Elsewhere in the region are juxtapositions never dreamed of a few decades ago—a Senor Chicken next to a Popeyes or a Chinese noodle house across the street from Hooters.

Langley Park, in Prince George’s County, has become an enclave of several hundred Salvadorans crowded into garden apartments. The local elementary school is more than 80 percent Latino. Young Latino men gather in a shopping-center parking lot hoping someone will come by to hire them for the day, and teenagers fill the aisles of the Ritmo Latino music store. On a Sunday as many as 50 vans are parked along the streets selling pupusas, a Salvadoran specialty, to crowds out enjoying a day off. But there also are reminders of work—another 50 trucks are loaded with the ladders that every painter needs.

Baileys Crossroads, in eastern Fairfax County, is another immigrant enclave. Traffic on Route 7 backs up on Friday afternoons because so many Muslims come for prayers at the Dar Al Hijrah mosque, which opened in 1991. More than half of the families at St. Anthony’s Catholic parish are Latino, and there are three masses each week in Spanish. And at Culmore Shopping Center a young man was stabbed to death by a teenager—both victim and perpetrator Latino.

That killing—along with three others in Langley Park last summer—were linked by police to local offshoots of the gang Mara Salvatrucha, more commonly known as MS-13. Several jurisdictions have added bilingual officers and established programs to keep immigrant youths out of trouble; one in Fairfax pays for tattoo removal for kids who want to give up gang life.

Immigrants have been subject to some political backlash. Fairfax County, Manassas, and Herndon have tried to prohibit overcrowding of houses that immigrants share. Other controversy surrounds the practice of immigrants, including illegals, waiting in parking lots to be picked up by employers looking for day laborers. In Herndon, a decision to use tax money to create a center for day laborers led to defeat at the polls for the mayor and two town-council members who supported the move.

Although packing up and moving to a strange country can be a lonely experience, Washington’s immigrants have social networks and institutions that bind them to other newcomers. Often it is these geographically dispersed ties, rather than living together in ethnic enclaves, that provide immigrants with the cultural moorings that make the assimilation into American society less jarring.

Some cultural ties revolve around restaurants, which bring the familiar dishes of the homeland to immigrants at the same time they introduce longtime residents to cuisines that were little known here 30 years ago. This year The Washingtonian’s 100 Best Bargain Restaurants had 65 such establishments. Among the selections: Thai, Cantonese, Szechuan, Indian, Vietnamese, Korean, Burmese, Malaysian, Bolivian, Taiwanese, Afghan, Persian, Lebanese, Pakistani, Mexican, Salvadoran, Peruvian, Ethiopian, Cuban, and Caribbean.

There also are plenty of small retailers who cater to immigrant communities, offering goods and services rarely seen by most native-born Americans. They range from food (goat meat, plantains, exotic spices) to traditional clothing and hairstyling to native-language music and movies. The Eden Center, a strip mall in Falls Church that has replaced Clarendon as the main shopping center for Vietnamese, has a supermarket, several restaurants, bakeries, a barbershop, video and music stores, a sports bar, a billiards parlor, jewelers, a travel agency, and a tax preparer. In Chantilly, a former Hechinger hardware store has been converted to a Korean shopping center that also has a martial-arts studio and is adding a lavish Korean-style spa.

Ethnic affinities are nurtured in dozens of other places. There are lively bars and nightclubs featuring karaoke, salsa, soca calypso, or reggae. Every year most immigrant groups have cultural festivals with parades, music, dancing, food, and crafts. Well-organized sports activities include everything from Latino soccer leagues to Asian tennis tournaments and Indian cricket matches.

Many ethnic newspapers—in Spanish, Korean, Chinese, Vietnamese, Arabic, and other languages—are available in restaurants and shops. Radio stations and cable television shows offer news and entertainment, and immigrants are increasingly using the Internet. IndiaDC.com directs people to Indian lawyers, doctors, beauty parlors, temples, books, and information-technology jobs. About 100 people have posted short bios on the Web site Hispanic Professionals Meetup Near Washington: “Hola amigos y amigas! I am an IT professional at Booz Allen in Tysons.”

Compared with 19th-century immigrants who booked steerage across the Atlantic and relied on handwritten letters to stay in touch with the old country, today’s immigrants live in a world that is closely linked by technology. Washington’s international airports—Dulles and Baltimore-Washington—have direct flights to and from El Salvador, Guatemala, Mexico, Ethiopia, Jamaica, and Tobago. Millions of dollars earned here are sent home to relatives by Western Union and other agencies, including El Salvador-based Bancomercio, which now has five area locations. Phone cards are available at liquor stores and convenience stores to call anywhere in the world. And some of the more successful immigrants make enough money here to build second homes in their native cities.

But there also are indications that Washington’s newest immigrants are repeating the age-old process of assimilation on which America pluralism has been built. Many of them, especially the young, are mastering English and becoming naturalized citizens. They’re learning to eat hot dogs on the Fourth of July and pumpkin pie on Thanksgiving. Parents are sending their children to college while worrying that they don’t stick with the traditional religion and are marrying outsiders.

They’ve begun running for political office. J. Walter Tejada, a member of the Arlington County Board, and Victor Ramirez, a member of the Maryland House of Delegates from Prince George’s, both came here as boys from El Salvador.

The newcomers are putting down roots, buying homes by the thousands, and, when the time comes, making the final commitment. I can see it happening in the cemetery behind my house in Arlington where most of the old stones tell stories of Graysons, Giraldis, Hoffmans, Kleins, and O’Shaughnessys. The names on the newer graves—Nguyen, Lopez, Wu, Torres, and Trang—speak of a Washington far more diverse than the black-and-white Washington of old.