The District's population grew nearly 2.2 percent to 632,323 residents last year as young workers flocked to the city, while its suburbs swelled because of increased immigration, according to census data released Thursday.

D.C.'s population is the largest it has been since 1980, when the census took population counts only once a decade. The increase was driven by 6,050 people who moved into the city from elsewhere in the United States between July 2011 and July 2012, according to census data. The increase almost matched Arlington's growth rate -- the county's population jumped by 2.3 percent to 221,045 in 2012, the fastest in the immediate Washington area.

Other counties saw their increases buoyed by immigration after seeing thousands of residents move out last year. Montgomery County brought in 8,659 international immigrants and lost 3,134 residents between 2011 and 2012, helping push the county past the 1 million-resident mark for the first time.

Moving in, moving out
Population, 2012 Population, 2011 Immigration, 2011-2012 Domestic migration, 2011-2012
D.C. 632,323 619,020 2,903 6,050
Montgomery 1,004,709 991,645 8,659 -3,134
Prince George's 881,138 874,045 6,077 -5,034
Fairfax 1,118,602 1,104,338 9,500 -4,919
Arlington 221,045 216,118 2,002 831
Alexandria 146,294 144,108 1,522 -1,238
U.S. Census Bureau

Fairfax County retained its spot as the most populous county in the region, growing to 1.12 million in 2012 with 9,500 new immigrants and 4,919 departures. Prince George's County, which grew by 0.8 percent to 881,138 residents, saw 5,034 residents move out and 6,077 immigrants move in.

The District's continued growth -- its population has risen every year since 2005 -- can be attributed to the steady flow of young professionals and the relative security of government and government-related jobs, even during the recession.

"People coming for those jobs want to be within the city itself," said Howard University sociology professor Roderick Harrison. "The lifestyle centers around what might be called the upscale consumption of residents -- restaurants, theater, live performance."

Brittany Kademian, who moved to Columbia Heights from Northern Virginia in 2010, said getting a job in D.C. meant "it was my time to move into the city."

"More and more people moved there and enjoyed living there, and now it is really overly congested with all sorts of people from every walk of life," Kademian said. "New businesses are popping up, but they are continuously being forced to creep further and further away from the main center of the neighborhood."

Not all suburban expatriates end up in the District, though. Even more end up moving further from the city to escape rising housing prices.

"The cost of housing has driven people to go further from the inner suburbs to find affordable housing," said Peter Tatian, a senior research associate at the Urban Institute's Metropolitan Housing and Communities Policy Center. "People have to go to the next ring out or even further."

Loudoun County was the country's 17th-fastest-growing county over the last two years, according to the census, with a population that jumped from 312,332 in 2010 to 336,898 in 2012. Prince William County, which grew from 402,002 residents in 2010 to 430,289 in 2012, ranked 31st.

Prince George's County Council Chairwoman Andrea Harrison said she sees residents trading shorter commutes for cheaper mortgages.

"We have a large amount of people moving from Prince George's County down to Charles County," she said. "It's even more affordable there."

Charles County's population jumped nearly 2.4 percent in the past two years, from 147,113 in 2010 to 150,592 in 2012.

While pricey housing can deter immigration, immigrants to the Washington area are often better-educated and make more money than their counterparts in other metropolitan areas, said Randy Capps, a senior policy analyst at the Migration Policy Institute. He expects immigration to continue driving suburban population growth.

"I don't think the trends have changed," Capps said. "If anything, they've intensified."