Using income and household relationship data from the American Community Surveys (ACS), the Census Bureau provides unofficial estimates of the number and percentage of people in poverty for sub-national levels of geography.
The Bureau produces ACS estimates for the nation, states, and large metropolitan statistical areas.
Frequency and Timespan: Annual data and averages across mulit-year timespans for 2004-2012
Geographic Level of Coverage: Subnational estimates of income and poverty for all places, counties, and metropolitan areas with a population of at least 65,000 as well as the nation and the states
Publications and Tables available online
U.S. Census Bureau. Description of Income and Poverty Data Source. (PDF) Accessed 2/14/2012