The number of African Americans residing in the District plummeted by more than 11 percent during the past decade, with blacks on the verge of losing their majority status in the city for the first time in half a century.

According to census statistics released Thursday, barely 50 percent of the District’s population was African American in 2010 — a remarkable shift in a place once nicknamed “Chocolate City.”

The black population dropped by more than 39,000 over the decade, down to 301,000 of the city’s 601,700 residents. At the same time, the non-Hispanic white population skyrocketed by more than 50,000 to 209,000 residents, almost a third higher than a decade earlier.

The census statistics showed a steeper change for both blacks and whites than had been estimated. With the city ‘s black population dropping by about 1 percent a year, African Americans might already be below the 50 percent mark in the city.

In a city that prides itself on being a hub of black culture and politics, a majority of residents have been black since whites began moving to the suburbs en masse at the end of World War II. By 1970, seven out of 10 Washingtonians were black.

The loss of blacks comes at a time when the city is experiencing a rebound, reversing a 60-year-long slide in population and adding almost 20,000 new residents between 2000 and 2010.

The demographic change is the result of almost 15 years of gentrification that has transformed large swaths of Washington, especially downtown. As housing prices soared, white professionals priced out of neighborhoods such as Dupont Circle began migrating to predominantly black areas such as Petworth and Brookland.

The city became a tougher place to live for working-class families, who had to contend with rising rents and soaring property taxes. Many of the new jobs created over the past decade have required higher education.

The phenomenon exposed the city’s fault lines along income, class and race.

“Clearly, D.C. is one of the most polarized cities, by income and education, in the country,” said Rodrick Harrison, a demographer at Howard University who spent 10 years with the Census Bureau.

“You have this unusually large college educated population. And then you have a population that is largely black, with high school degrees or less.”

Maurice Jackson, a professor of African American history at Georgetown University, said the black middle class has followed the white middle class before them, heading to the suburbs in search of more affordable housing and good schools.

“No opportunities are being created for low- and middle-income people in the city,” he said. “I drive to Georgetown ever day, and very rarely do I see African Americans on construction jobs.”

Some say the precipitous decline in the number of African Americans is alarming.

“We’re going to stop this trend — gentrification,” said D.C. Council member Marion Barry (D-Ward 8). “We can’t displace old-time Washingtonians.”

“The key to keeping this city black is jobs, jobs, jobs for black people so they can have a better quality of life in neighborhoods in the city,” he added. “I believe in integration, but I don’t believe in the apartheid we have in Ward 8. You don’t see corner stores in Ward 3. You don’t see the liquor stores.”

Barry, the four-term mayor who emerged from the civil rights movement, also faulted Congress for overturning a residency requirement for local government workers in 1988. That, he said, helped build up what he called “Ward 9,” referring to Prince George’s County.

“We can’t keep people from moving, but if we had a residency requirement, we could keep government workers from moving,” Barry said.

Anthony A. Williams said that, during his two terms as mayor, he made a concerted effort to attract new residents and businesses to pay taxes and generate revenue for a city in decline.

“When you’re the mayor, you’re not God,” Williams said. “It’s very frustrating. When you’re in public service, you’re there to promote diversity and harmony, but on the other hand, you want to help your city economically. Sometimes, they come at cross purposes.”

Williams said he believes African American culture will continue to be the dominant culture in the city. But others say they already see it slipping away.

“The Parliament song ‘Chocolate City’ pinned a label on the city,” said poet E. Ethelbert Miller, a leading figure in Washington’s African American arts community. “Well, chocolate melts.”

Miller laughed, then turned serious. “We’re seeing the eroding of a community. If you’re a black person accustomed to a way of life, that way of life is coming to an end. The city ain’t gonna be black no more. ... This is the Vincent Gray era, and that’s symbolic. The city is stuck in gray now. We’ll mourn that Chocolate City is gone, but that’s just the nature of it.”

Staff writers DeNeen Brown, Henri E. Cauvin, J. Freedom du Lac, Annie Gowen, Paul Schwartzman, Nikita Stewart and Ovetta Wiggins contributed to this report.