The emergence of police accountability as an issue of concern in communities across the nation has led to a watershed era in the evolution of accountability systems involving civilian oversight of municipal police agencies. This Article reports on a survey of the civilian oversight entities in the one hundred most populous U.S. cities and draws on recent trends it identifies to illuminate the challenges inherent in civilian oversight of police. This Article is intended to serve as a resource for civilian oversight professionals as well as local government and community leaders who are advocating for new or revised oversight systems