This paper builds on a series of ANF publications that explored various aspects of social policy federalism since 1996. It explores what ANF's work can tell us about the evolution of federalism within five major social programs during the nine years between 1997 and 2006, focusing on lessons about federal-state relationships. It addresses Temporary Assistance for Needy Families (TANF), Food Stamps, Medicaid, the State Children's Health Insurance Program (SCHIP), and child welfare. The paper is the result of a review and synthesis of over 65 publications addressing state and federal financing and/or programmatic arrangements in the major program areas, informed by interviews with experts who participated in ANF research.