In this chapter, we provide a comprehensive overview of the evolution of state security forces in the region, from independence until the end of the Cold War. We show the dramatic evolution of these forces from informal militia with little training to a vast network of professional agencies with defined spheres of responsibility. We begin this chapter by examining the state security forces that developed in the decades following independence in a period dominated by caudillo politics. We then discuss the gradual professionalization that took place in the late 1800s and early 1900s as part of a broader process of national consolidation and centralization. The United States then played an integral role in shaping state security forces beginning in the early 1900s in Central America and the Caribbean and then after World War II in the rest of the region. During the Cold War, most countries in the region were under authoritarian rule, and the United States helped them to expand the size of their state security forces, spurred the creation of specialized agencies, and shifted the overall focus of state violence further toward combatting domestic threats.