Today, free public kindergarten for five-year-old children is available in every state and community throughout the United States, and public education is routinely referred to as K-12. But kindergarten did not start out this way. Kindergartens in the United States once served children as young as three and four years old. In fact, today’s movement for public pre-kindergarten (pre-K) is a consequence of the gradual exclusion of almost all three- and four-year-olds from public kindergarten. A century ago, the U.S. kindergarten landscape looked similar to preschool today. Kindergarten had limited public funding and was predominantly composed of private programs paid for by families and charitable donations. It took more than a hundred years to establish kindergarten as a public good. (author abstract)