The Earned Income Tax Credit (EITC) is the cornerstone U.S. anti-poverty program, typically lifting over 5 million children out of poverty each year. Targeted to low-income households with children, and only available to those who work, the EITC contains strong incentives for non-workers to become employed. Most of the existing economics literature focuses on federal EITC expansions in the 1980s and 1990s. This paper takes a longer view, studying all federal expansions since the program's inception in 1975. We find robust evidence that EITC expansions increase the extensive margin of labor supply.