Using income and household relationship data from the American Community Surveys (ACS), the Census Bureau provides number  and percentage of people in poverty for the nation, states, and large metropolitan statistical areas. 

Frequency and Timespan: Annual data and averages across mulit-year timespans for 2004-2010

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

Source:  U.S. Census Bureau. Description of Income and Poverty Data Sources. Accessed 2/14/2012