Final answer:
The first federal social welfare program was the Aid to Families with Dependent Children (AFDC), established during the Great Depression to provide aid to mothers with children below the poverty line.
Step-by-step explanation:
The first federal social welfare agency to provide aid to the poor was the Aid to Families with Dependent Children (AFDC) program. Established during the Great Depression, this program provided cash assistance to mothers with children below the poverty line. Although local and state efforts existed in various forms, such as Governor Franklin D. Roosevelt's Department of Welfare in New York, the AFDC represented a significant expansion in aid at the federal level. The AFDC operated until 1996 when it was replaced by the Temporary Assistance for Needy Families (TANF) program as a result of the welfare reform act signed into law by President Bill Clinton.