Governmental public health activities in the United States have evolved over time as a result of two forces: the nature and perceived importance of threats to the population's health and safety, and changing relationships among the various levels of government. Shifts toward a more state-centered form of federalism in the second half of the twentieth century weakened key aspects of the governmental public health enterprise, including its leadership and coordination, by the century's end. These developments challenge governmental public health responses to the new threats and increased societal expectations of the early twenty-first century.Many are the exercises of power reserved to the States wherein a uniformity of proceeding would be advantageous to all. Such are quarantines and health laws. 1
Thomas Jefferson, 1807T h e f e d e r a l i s t s ys t e m of American government, marked by the distribution of responsibilities among its national, tribal, state, and local components, is an essential contributor to our public health aspirations. Each component contributes in various ways, and to varying degrees, to assessing, addressing, and assuring conditions in which people can be healthy. Although constitutional and legal frameworks define the basic functions and roles of the various levels of government, an even more complex web of intergovernmental relationships characterizes the operational aspects of federalism. 2 These operational relationships influence the ability of the overall governmental public health enterprise to protect and promote the health of the public.To a large degree, the organization, financing, and delivery of public health ser-