Post-9/11, preparedness planning has catalyzed intrastate regionalization of local public health resources throughout the United States. Investigating this trend unveils several regionalization themes, relevant in other sectors of government, which are applicable to local public health. In this review article, we begin by briefly examining the lessons learned from regionalization for police and fire services, drawing comparisons to public health. Then we provide a brief history of the accelerating regionalization of local public health services sparked by the current attention to emergency preparedness. In particular, we offer case studies from Massachusetts and the National Capital Region to highlight examples of regionalization outcomes related to networking, coordination, standardization, and centralization of public health services. The impact of social capital on preparedness is also explored. Finally, we summarize research needs for the future.