The Washington region houses six of the nation's 10 richest counties, for an increase over last year's rankings thanks to climbing incomes here as other areas falter in their recovery from the recession.

Northern Virginia added to its hold as the richest area in the nation as Arlington County's median household income crossed the $100,000 threshold in 2011, according to survey figures released by the U.S. Census Bureau on Thursday. The county became the third-richest in the nation, joining Loudoun and Fairfax, which kept their respective No. 1 and No. 2 ranks from 2010.

Loudoun's median household income was $119,134, far higher than Fairfax's $105,797, although Loudoun's income slipped 0.3 percent, within the survey's margin of error.

The top 10
Rank County 2011 median household income 2010 median household income Change
1 Loudoun County $119,134 $119,540 -0.34%
2 Fairfax County $105,797 $103,010 2.71%
3 Arlington County $100,735 $94,986 6.05%
4 Hunterdon County, N.J. $99,099 $97,874 1.25%
5 Howard County $98,953 $101,771 -2.77%
6 Somerset County, N.J. $96,360 $94,270 +2.22
7 Prince William County $95,146 $92,655 2.69%
8 Fauquier County $93,762 $85,614 9.52%
9 Douglas County, Colo. $93,573 $94,909 -1.4%
10 Montgomery County $92,909 $89,155 4.21%

Virginia's Fauquier County also made the top 10, ranking eighth as its median household income jumped 9.5 percent to $93,762.

Montgomery County's median household income rebounded to nearly $93,000, and the county took 10th place after slipping out of the top 10 in 2010. Howard County fell below $100,000 for the first time since 2006; however, experts note that the drop is within the survey's margin of error.

Statewide, Maryland maintained its status as home to the richest households in the nation with a median income of about $70,000. Median household income in Virginia is nearly $62,000.

"This region is a place where there's been lots of job growth over the last five years," said Lisa Sturtevant, an assistant research professor at George Mason University's Center for Regional Analysis. "And these are jobs in the sectors that we were strong in already -- and those are high-wage jobs."

According to her research, Arlington's income growth also has jumped in recent years because households with annual incomes of less than $70,000 are moving to elsewhere in the region, she said.

The same is true for the District, which has seen an influx of wealthier households as lower-income ones have left. Over the last five years, D.C.'s median household income has increased by nearly 22 percent to more than $63,000 -- the largest jump of any jurisdiction in the region.

Maryland's Washington suburbs have fallen behind Northern Virginia's economic growth in recent years. And although Montgomery County's median household income increased by 4.2 percent last year, some say that doesn't mean the Maryland suburbs will start gaining ground on their rivals across the Potomac.

"Montgomery County simply couldn't keep getting worse," said Richard Clinch, director of economic research at the University of Baltimore's Jacob France Institute. "At some point, the ball bounces back up."

Clinch said Maryland's economy has not been as diverse as Northern Virginia's and still relies too heavily on business generated by the federal government. Incomes are starting to improve again, but Montgomery has some catching up to do.

Over the last five years, household incomes in Loudoun, Arlington and Prince William counties have posted double-digit growth. But in Montgomery, incomes have grown by 6 percent over the last five years, and Prince George's County incomes have grown by 7 percent since 2006.

"The worst has passed, and people are starting to see jobs and earnings again," Clinch said of suburban Maryland. "It isn't that it's growth mode; it is in slow and steady recovery."

Still, the region has enjoyed a relatively steady economic climate while the rest of the country has been stymied. According to the new data, the median income nationally is worse now than it was during the recession.

Median income for U.S. households increased by just 1 percent to $50,502 in 2011, a 3 percent drop from income in 2008, the year the recession began.