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 three-part 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. [For related briefs, see "Building the Child Wellbeing Project: Practitioners' Perspectives on the Role of Implementation Science in Strengthening Post-Care Child Welfare Services. Research-to-Results Brief. Publication #2012-18" (ED534867) and "Using Implementation Science to Support and Align Practice and System Change: A Case Study of the Catawba County Child Wellbeing Project. Research-to-Results Brief. Publication #2012-17" (ED534865).]