But a big chunk of that healthy income goes toward maintaining the good life. Loudoun homeowners pay a median $4,844 per year in property taxes. Tax burdens are similarly high in a lot of well-off counties. Like Loudoun, a number of the country's wealthiest households are tightly concentrated in counties around the nation's capital. Six of the richest counties lie on the outskirts of Washington: Fairfax County, Va., Arlington County, Va., Stafford County, Va., Prince William County, Va., Charles County, Md., and Alexandria City, Va.

Not far from D.C. lies another cluster of wealthy counties. Howard County, Md., a suburb of Baltimore, has a standout school system with standardized test scores that consistently beat out the national average, and median household incomes of $101,710. In nearby Montgomery County, where 59% of residents over 25 have an advanced degree, households bring in a median $93,999. Historic Calvert County, Md., has profited from its roots as a tobacco-rich farmland as well as its proximity to Washington, D.C., and Baltimore, and claims a median income of $89,049.

The suburbs of the New York area reap the benefits of the big city's financial industry. Six of the wealthiest counties in the country -- Hunterdon County, N.J., Somerset County, N.J., Morris County, N.J., Nassau County, N.Y., Putnam County, N.Y. and Suffolk County, N.Y. -- are all part of the New York metropolitan area.

These counties may be knocked a few rungs down the list when the next American Community Survey is released later this year. The new data will reflect incomes for 2009, when the near-collapse of Wall Street stripped many families in the city -- and its wealthy outlying suburbs -- of their paychecks.

While big-city life may seem glamorous, the rule that it's the boring old 'burbs outside of moneymaking metros where the highest incomes are found also applies far beyond the East Coast. Median incomes are highest in counties outside big cities driven by growth industries such as health care, technology and government.

Counties No. 18 and 19 on the list are two wealth centers in California: Marin County and Santa Clara County. Picturesque and stylish Marin offers scenic vistas, health care industry and technology industry money -- Kaiser Permanente and Comcast are among its major employers -- and a median income of $88,101. Well-paid, highly skilled tech jobs boost the median income to $87,287 in Santa Clara.

Nashville, Tenn., suburb Williamson County and Atlanta, Ga., suburb Forsyth County are the South's only representatives--but just like the other counties on our list, they have big-city growth industries to thank for their prosperity.

Nashville may be best known for country music, but it's the heavy-hitting health care giants like Hospital Corporation of America headquartered there that account for locals' wealth. Many workers in that booming industry take their paychecks home to Williamson, which has a median income of $88,316.

Beneficiaries of the jobs that companies like UPS, Coca Cola and Delta Airlines created in Atlanta have increasingly taken up residence in Forsyth, fueling a 71% population boom between 2000 and 2008 and helping drive the area's median income up to $86,938.

It makes sense that suburban median incomes tend to beat out big cities; workers earning big metropolitan incomes look for top-tier schools and space to settle with their families, thus pulling up median incomes in small bedroom communities. It also helps if those city economies are linked to growth sectors with lots of highly-skilled workers.

County: Loudoun County, Va.
Population: 277,433 - Median Household Income: $110,643.00
Percent of Residents 25 or Older with Bachelor's Degree or Higher: 58

County: Fairfax County, Va.
Population: 1,005,980 - Median Household Income: $106,785.00
Percent of Residents 25 or Older with Bachelor's Degree or Higher: 60

County: Howard County, Md.
Population: 272,412 - Median Household Income: $101,710.00
Percent of Residents 25 or Older with Bachelor's Degree or Higher: 60

County: Hunterdon County, N.J.
Population: 129,000 - Median Household Income: $100,947.00
Percent of Residents 25 or Older with Bachelor's Degree or Higher: 52

County: Somerset County, N.J.
Population: 321,589 - Median Household Income: $100,207.00
Percent of Residents 25 or Older with Bachelor's Degree or Higher: 53