Wealth in the United States - Concentrated in the Northeast

At the county level, America is a tremendously unequal place. The median household income in the poorest county (Wilcox County, Alabama) was $22,126 in 2012. In Falls Church, Virginia, where highly educated defense contractors and federal government workers cluster, the median income last year was $121,250, more than five times higher.
What's most startling, though, in new local income and poverty data released this week by the Census Bureau, is the way these opposing poles of poverty and wealth in America concentrate geographically. The Census map below shows median household income data from 2012 for every county in the country:

2012 Median household income by county.
There are more than 3,000 counties in the U.S. Of the 75 with the highest incomes, 44 are located in the Northeast, including Maryland and Virginia. The corridor of metropolitan statistical areas that runs from Washington, D.C., through Baltimore, Philadelphia, New York and Boston includes 37 of these top-earning counties (where the median family takes home at least $75,000 a year). Zoom in to the region, and it shows a kind of wealth belt unmatched even on the West Coast.
Poverty is similarly concentrated in the American South. Seventy-nine percent of the poorest counties in the country (where the median family makes less than $35,437) are located in the South: