Research from numerous disciplines provides support for the critical importance of early childhood development in economic development. The long-term individual and societal benefits of investing resources during early childhood make it an unrivaled opportunity for policy. Over the past 30 years, states have gained increasing control over the major policies for families with young children through the devolution of federal programs to states. States have also expanded their innovation and adoption of early childhood education programs during this time, such as prekindergarten. Policy makers need to understand how the differences in these policies across states affect policy effectiveness and child well-being, yet there is limited research, especially during early childhood. This article outlines the federally-devolved and state-developed policies for families with young children and the dimensions and characteristics that vary between states, and concludes with implications for research in the experimental arena of state-level policy. (author abstract)