Arlington is the richest county in America, according to one metric measured by the U.S. Census Bureau.

Arlington’s median family income in 2012 was $137,216, putting the county comfortably in first place over the country’s second-richest county, Loudoun County (Va.), at $127,192.

Arlington’s median family income grew by more than $5,000 since 2011, when it stood at $131,890, and more than $10,000 since 2007, when it was $127,179.

Howard County (Md.), is the third-wealthiest county in America at $125,152, according to the Census Bureau, and Fairfax County (Va.) is fourth at $124,831. Montgomery County (Md.) ranks seventh, with a median family income of $113,588. In all, nine D.C. area counties had incomes above $100,000, the highest of any metropolitan area.

Arlington’s income data does come with the caveat of a $10,561 margin of error.

The census data differs from another commonly used ranking, median household income, which placed Arlington third in the nation, well behind Loudoun and Fairfax, based on 2011 data.