This policy report by the Wallace Foundation seeks to support states and school districts in building comprehensive and aligned “principal pipelines.” While school districts have the most direct influence on principals, state policy sets the environment that affects how school principals emerge, develop, and practice. Thus, to understand how to create and sustain excellent principals—referred to as the “principal pipeline”—one must account for local district and state policy. To support the principal pipeline, seven domains must be met. Each pipeline must demonstrate: (1) rigorous standards, (2) high-quality preservice preparation, (3) selective hiring and placement, (4) on-the-job evaluation and support, (5) growth-oriented supervision, (6) leader tracking systems, and (7) systems to sustain such efforts. The report dives deeper into the state–district nexus, identifies state and local vantage points in creating excellent principals, offers policy levers pertaining to each domain, and provides questions for state and local leaders to consider. This resource works to help state and district policy leaders, as well as principal preparation administrators, ensure that all schools bring on excellent principals and have practices in place to support them on the job.