The Richest Counties in America The U.S. may be still struggling with the Great Recession’s effects, but that doesn’t mean that every part of the country is struggling. In fact, many Americans are living well above the poverty line. But where exactly are they? by MainStreet | Nov 10, 2010 1:45 PM EST #10: Charles County, Md. #9: Calvert County, Md. #8: Somerset County, N.J. #7: Nassau County, N.Y. #6: Montgomery County, Md. #5: Arlington County, Va. #4: Morris County, N.J. #3: Howard County, Md. #2: Fairfax County, Va. Richest County: Loudoun County, Va.