Over the last decade the power of states to develop more effective policies and programs to improve the well-being of children has been substantially strengthened by the increasing availability of high quality child well-being indicator data at the state level. Much of these data have been developed by or under the guidance of federal statistical agencies. The authors believe it is a good time to take stock of the strengths of the existing data collection system, and to identify opportunities to improve that system in ways that will better serve the needs of children and the policy makers who serve them. In this paper they provide an overview of Federal sources of social indicator data on children's well-being that provide estimates at the state-level, that is, for children in individual states. Twenty-one major survey and administrative data sources are summarized and discussed. Areas of strength are identified, as are important gaps and opportunities for future development. In addition, they provide an appendix that includes systematic one- to two-page summaries for each of the data sources reviewed for purpose, content, and periodicity. (Contains 2 tables and 18 footnotes.)