Over the past 70 years, all states in the United States began to publicly subsidize kindergarten using state revenue. The variation in adoption dates across states allows for a unique opportunity to measure the effectiveness of the largest early education program implemented in recent history. The significant, immediate increase in the availability of kindergarten within a state is used to identify the effect of enrollment in kindergarten. Hispanic children, non-English speakers, children from immigrant households, and children of low socioeconomic status benefit the most from the increased availability of kindergarten. Hispanic children with access to kindergarten are 17% less likely to be below grade for their age and earn wages 5% higher as adults. (Contains 29 notes, 6 tables, and 2 figures.)