Background: 2007-2013 spanned an economic downturn with rising food costs. While Supplemental Nutrition Assistance Program (SNAP) benefits increased during those years by 13.6% from the 2009 American Recovery Reinvestment Act (ARRA), the impact of these competing conditions on household food insecurity (HFI, household food insecure but child food secure) and child food insecurity (CFI, household and child food insecure) in households with infants and toddlers has not been investigated. Objective: To describe HFI and CFI in households participating in SNAP vs. households likely eligible but not participating (No SNAP). Design: Repeat cross-sectional. Participants/Setting: 19,999 caregivers of children. Children's HealthWatch survey in emergency and primary care departments in 5 US cities. Main Outcome Measures: The 18-item U.S. Household Food Security Survey (HFSS) measured HFI (=3 affirmative responses on non-child-specific questions) and CFI (=2 affirmative responses to eight child-specific questions). Statistical analyses performed: The sample was stratified by SNAP/No SNAP. Multinomial logistic regression analyses examined the association between SNAP receipt and HFI and CFI. Results: Across the study period, controlling for confounders including year, households with SNAP were 17% less likely to experience HFI (AOR 0.83; 95% CI, 0.75, 0.91) and children in households participating in SNAP were 33% less likely to experience CFI (AOR 0.67; 95% CI, 0.60-0.74) than children in the No SNAP group. Conclusions: Receipt of SNAP vs. No SNAP was associated with decreased prevalence of HFI and CFI during much of the economic downturn; this impact waned as the buying power of the boost in benefit amounts during the ARRA period eroded.