This paper estimates the long-run effects of childhood Medicaid eligibility on adult health and economic outcomes using the program’s original introduction ( 1966–1970) and its mandated coverage of welfare recipients. The design compares cohorts born in different years relative to Medicaid implementation, in states with different preexisting welfare-based eligibility. Early childhood Medicaid eligibility reduces mortality and disability, increases employment, and reduces receipt of disability transfer programs up to 50 years later. Medicaid has saved the government more than its original cost and saved more than 10 million quality adjusted life years. (JEL H51, I12, I18, I32, I38, J13)