In October 2006, the United States Census Bureau released data about the median family income of families in all counties within the United States and Puerto Rico. The data was released in the Bureau's Annual Community Survey (ACS) report. The median family income (in 2005 Inflation-Adjusted Dollars) represents the mid-point of family income for a county, where half of the families are above the median value, and half of the families are below the median value. The median value measurement is sometimes a better indicator than average value because it is less susceptible to unusually high or low values.

Listed below are the top 15 counties with the highest median family income, followed by the median value dollar amount, and the State.

1. Loudoun County - $110,910 (Virginia)
2. Fairfax County - $110,107 (Virginia)
3. Arlington County - $106,218 (Virginia)
4. Hunterdon County - $106,167 (New Jersey)
5. Somerset County - $105,872 (New Jersey)
6. Howard County - $103,390 (Maryland)
7. Morris County - $100,971 (New Jersey)
8. Marin County - $99,713 (California)
9. Douglas County - $99,531 (Colorado)
10. Montgomery County - $98,662 (Maryland)
11. Williamson County - $95,470 (Tennessee)
12. Calvert County - $93,842 (Maryland)
13. Monmouth County - $92,080 (New Jersey)
14. Nassau County - $91,349 (New York)
15. Rockland County - $90,947 (New York)

As noted above, Virginia occupied the top 3 slots on this list. New Jersey had 4 counties within the top 15. Maryland had three counties in the top 15. New York had 2 counties in the top 15. Surprisingly, California only had 1 county in the top 15, which was Marin County located just north of San Francisco. The median family income for United States as a whole was $58,832.

If you are interested in buying a home, condo or townhouse or any other type of real estate, you should know that the median family income of a region is sometimes used by lenders to determine if a family is eligible for special low-income loan programs.

For detailed ranking tables of all counties within the United States, visit the Census Bureau's web site, and select the most recent American Community Survey report. The American Community Survey report is published annually.