This presentation will discuss the increase in public insurance eligibility caused by the Affordable Care Act (ACA) Medicaid expansions may have had spillover effects to other public assistance programs. We explore the impact of the ACA on participation in the Earned Income Tax Credit (EITC), the Supplemental Nutrition Assistance Program (SNAP), and Temporary Assistance to Needy Families (TANF). Our research design uses variation in Medicaid eligibility that occurs on either side of state borders: we examine program participation in contiguous county pairs that cross state lines using both county level administrative data and individual data from the American Community Survey (ACS). This approach allows us to focus narrowly on differences arising from the ACA Medicaid expansion choice, implicitly controlling for local economic trends that could affect safety net participation. Our results suggest that the Medicaid expansion increased participation in SNAP and TANF, and possibly in the EITC. The ACS analysis suggests that safety net impacts are mainly due to participation conditional on eligibility rather than from eligibility changes stemming from labor supply responses. It appears that ACA Medicaid eligibility reduced the marginal cost of applying in SNAP, particularly facilitating enrollment in places with low 2013 SNAP take-up rates. Our results demonstrate the potential for spillovers across safety net programs.