The first eight years of life, beginning before birth and continuing through third grade, are a critical developmental period that sets the stage for future success. Research over the past 15 years has demonstrated the importance of high-quality care and education throughout the prenatal-through-third-grade (P-3) continuum, including prenatal and infant and toddler care, preschool education, and early elementary education. The programs and services provided to young children and their families during these early years are typically highly fragmented in most communities in the United States, the result of a multiplicity of funding streams and the wide variety of early education settings, services, and professional roles that characterize the mixed-delivery system in the United States. Communities, states, and the federal government are all working to improve quality and coherence across the P-3 continuum. This report provides three case studies to address a central question: How can states support P-3 system building at both state and local levels? The three case-study states--Massachusetts, Oregon, and Pennsylvania--were chosen based on their experience implementing P-3 state policies and developing significant grant programs to fund regional and local P-3 partnerships. The case studies profiled in this report demonstrate the crucial roles State Education Agencies (SEAs) can play in supporting P-3 system building--both through state policy as well as by supporting local and regional early learning partnerships. Carrying out this work requires that SEAs align their work internally across divisions and units while building the capacity of communities to design and implement quality improvement and alignment activities.