There are 3,033 counties in the United States. Which 10 are the richest in terms of median household income? Not surprisingly, those near major economic centers rank high.

In a study based on household income estimates from the Census Bureau’s American Community Survey, Loudoun County, Virginia captures the number one spot in America’s Richest Counties.

Loudoun County is a Washington, D.C. suburb and is home to Dulles International Airport, as well as a well-educated workforce.

The complete Top 10 list of America’s Richest Counties :

1. Loudoun County, Virginia ($115,574)
2. Falls Church City, Virginia ($114,409)
3. Fairfax County, Virginia ($105,416)
4. Los Alamos County, New Mexico ($103,643)
5. Howard County, Maryland ($103,273)
6. Hunterdon County, New Jersey ($100,980)
7. Douglas County, Colorado ($99,198)
8. Fairfax City, Virginia ($97,900)
9. Somerset County, New Jersey ($97,440)
10. Morris County, New Jersey ($96,747)

As a region, it’s estimated that 40% of the Washington, D.C. metro area economy can be attributed to federal spending. This helps explain why Falls Church City, Virginia; Fairfax County, Virginia; and Howard County, Maryland all scored high on the list. It’s also why Los Alamos ranked 4 — the largest employer in Los Alamos is the Los Alamos National Laboratory, one of the largest science and technology institutes in the world.

The New Jersey counties are popular commuter areas for homeowners who work in New York City.

As a home buyer , the wealth of particular area may matter to you, but it won’t be the sole reason you purchase. You may have interest in a quality school district, or a vibrant nightlife, or a a high walkability factor, for example.

For more detailed statistics about the 10 counties at top or other local markets, be sure to ask your real estate agent.