[edit] 2011

The rankings are based on the median annual household income estimates from 2005 to 2009 in each county in the nation, provided by the 2011 U.S. Census' American Community Survey.^[1][2] Since cities in Virginia are independent of surrounding counties they are included in the Census Bureau's ranking.

Number of counties by state in following list: Virginia 5 plus 3 independent cities, Maryland 4, New Jersey 3, New York 3, California 2, Colorado 1, Georgia 1, New Mexico 1, Ohio 1, Tennessee 1. Of the top 25 counties, 10 are part of the Baltimore-Washington Metropolitan Area, 6 counties are part of the New York Metropolitan Area, and 2 counties are part of the San Francisco Bay Area. By Census region, 14 counties are located in the South, 6 in the Northeast, 4 in the West, and 1 located in the Midwest. 17 of the 25 counties are part of the densely-populated Northeast Megalopolis.