This is the first brief in a series, Building a Post-Care Service System in Child Welfare: Lessons Learned from the Frontlines of Implementation Science in Catawba County. This brief sets the stage for a threepart series on the Catawba County Child Wellbeing Project by describing the Project’s origins and historical context. Topics include: 1) the purpose of building a post-care service system; 2) the needs of post-care children and families; and 3) the guiding theory of change for the development, implementation, and evaluation of the Project. Additionally, the brief discusses the roles of various organizations involved with the Project – The Duke Endowment, the Catawba County (North Carolina) Department of Social Services (usually called Catawba County Social Services), the National Implementation Research Network and Independent Living Resources, Inc.