The purpose of this project was to evaluate the effect of a natural experiment in the City of Saint Louis on physical activity levels in a primarily low income, African American neighborhood. The study neighborhood underwent significant revitalization efforts, including the addition of mixed-use development, rehabilitation of parks, streetscape enhancements, and the construction of a walking/biking trail. The project measured physical activity levels before and after the environmental changes to determine whether children's overall activity levels are higher after the revitalization effort. The built environment was measured using objective measures, and parental self-report measures assessed physical activity levels.