Major sources of poverty data are available from the Department of Health and Human Services (DHHS) and from the U.S. Census Bureau. However, the DHHS and Census measurements and definitions are not identical. Make sure your terms and sources are clearly defined.
From DHHS:
DHHS Poverty Guidelines (with links to other useful data)
History of Poverty Measurement at DHHS
DHHS FAQ page on Poverty Guidelines
DHHS 2015 Poverty Guidelines
From the U.S. Census:
How the Census Bureau Measures Poverty
Poverty Data
Poverty Thresholds since 1959
How the Census Measures Poverty
Comparing American Community Survey (ACS) Data