In spring 2024, the authors surveyed 156 American School District Panel member districts about principal pipeline activities across seven domains -- leader standards, principal preparation, selective hiring and placement, on-the-job support and evaluation, principal supervision, leader tracking systems, and systems of support -- to estimate the share of U.S. public school districts engaged in such activities. Researchers also examined those activities by district enrollment size to investigate the hypothesis that the infrastructure to support the principal pipeline is mostly confined to large districts. This report is intended to support administrators of principal preparation programs, school district leaders, state department of education staff who oversee principal certification and leadership development, and education researchers who study school leadership.