We derived America’s wealthiest locales from the Census Bureau’s latest American Community Survey, released in December 2011, which measures median household income as of the end of 2010. The survey breaks down the country into more than 29,000 cities, towns, villages and what the Census Bureau calls CDPs (Census Designated Place – a small area within a larger town or city with no local government of its own but which otherwise resembles a town).

http://www.forbes.com/sites/tomvanriper/2012/02/13/americas-most-affluent-neighborhoods/