Rich Blocks, Poor Blocks - From Crain's Chicago Business

An interactive map making the rounds on the Web provides a fascinating look at wealth inequality in cities across the United States. The map, called "Rich Blocks, Poor Blocks," was created by Chris Persaud, an editorial research specialist. Mr. Persaud mapped out the median incomes in every census tract in every city in the U.S. (A census tract usually consists of between 2,500 and 8,000 people.) 

http://www.richblockspoorblocks.com/