Publisher Summary This introductory chapter introduces the relationship between public health and emergency management in the development of the U.S. preparedness infrastructure. The U.S. National Preparedness Guidelines are based on federal, state, and local preparedness capabilities that are generated through the use of 15 National Planning Scenarios. The scenarios are used for training and exercises to identify and assess Universal Tasks and Target Capabilities at each level of the government. This is the structure by which preparedness is developed and evaluated in the United States. However, public officials do not have the capacity to meet the needs arising from major disasters without the assistance of volunteer organizations and the cooperation of the public. A key aspect of public and volunteer engagement is social capital. This interconnectedness of community networks has waned in recent years and to effectively manage a major incident, it needs to be reignited. In addition, citizens must be motivated to take simple measures such as completing a plan, preparing a kit, and following the advice of officials. These steps mitigate the severity of major disasters and sustain the physical and mental health of those affected by catastrophe.