The essential role of physical activity both as an independent protective factor against numerous common chronic diseases and as a means to maintain a healthy weight is gaining increasing scientific recognition. Although the science of physical activity promotion is advancing rapidly, the practice of promoting physical activity at a population level is in its infancy. The virtual absence of a public health practice infrastructure for the promotion of physical activity at the local level presents a critical challenge to control policy for chronic disease, and particularly obesity. To translate the increasing evidence of the value of physical activity into practice will require systemic, multilevel, and multisectoral intervention approaches that build individual capability and organizational capacity for behavior change, create new social norms, and promote policy and environmental changes that support higher levels of energy expenditure across the population. This paper highlights societal changes contributing to inactivity; describes the evolution and current status of population-based public health physical activity promotion efforts in research and practice settings; suggests strategies for engaging decision makers, stakeholders, and the general public in building the necessary infrastructure to effectively promote physical activity; and identifies specific recommendations to spur the creation of a robust public health infrastructure for physical activity.