State Defense Forces (SDFs), or organized state militias and naval militias, have a long and distinguished history of service in the United States. These state-sanctioned organizations are substantiated and legitimized through the U.S. justice system and constitutional law. Currently, 23 states and U.S. territories have SDFs; unlike National Guard units, they cannot be federalized, which means they remain a state-level asset during emergency management operations. SDFs were utilized successfully during Hurricane Katrina, proving their value in state and federal emergency response efforts. This book seeks to analyze the structure and usefulness of the SDF as a volunteer emergency response organization. Second, it seeks to understand the evolution of the SDF by examining U.S. militia history. Third, it examines the disaster-relief efforts of SDFs with regard to Hurricane Katrina. SDFs provide state governors with emergency response personnel who are locally available and ready to serve in multiple capacities. Presently, state officials can promote legislation and develop a mission-flexible State Defense Force that can act as a reserve force for local law enforcement and the National Guard during natural and man-made disasters. The SDF may be the next step in the evolution of state and local emergency response in the 21st century.