State policy contributes to the overall environment that affects how school principals emerge, develop, and lead their schools. School districts are most proximate to the work that principals do and therefore have the most direct, regular engagement with candidates for the principalship, principals in training, and principals on the job. As a result, to understand the multiple processes that bring excellent principals into schools and support them on the job--metaphorically, the "principal pipeline"--one must account for local and state forces. This paper examines the nexus where state and local actions come together to develop and support excellent principals. It describes key policy levers that state officials can pull as they support the work of local officials as they work to develop comprehensive and aligned principal pipelines. Along the way, the paper offers key questions that state and local officials and their policy partners can ask in order to assess their strengths and weaknesses as they work together, leveraging their comparative advantages, to ensure that all schools have excellent principals.