Americans' health improved dramatically over the twentieth century. Public health programs for disease and injury prevention were responsible for much of this advance. Over the century, America's public health system grew dramatically, employing science and political authority in response to an increasing array of health problems. As the disease burden of the old scourges of infection, perinatal mortality, and dietary deficiencies began to lift, public health's mandate expanded to take on new health threats, such as those resulting from a changing workplace, the rise of the automobile, and...