The first three years of a child’s life lay the foundation for all subsequent health and development. State policy leaders are increasingly convinced by the science of the developing child that early intervention is prudent, but they need guidance on which state policies are most effective at creating the conditions in which children thrive. This chapter discusses the similarities and differences in identifying effective policies as compared to effective programs, details the process of identifying effective policies, and provides recommendations for policy makers to create an evidence-based policy agenda to strengthen the prenatal-to-3 system of care.