A recent National Park Service (NPS) report identified the importance of effectively engaging communities of color in order for nation-al parks to remain relevant in an increasingly diverse American society (CSI 21st Century Rel. Report). This report laid the foun-dation for exploratory evaluation research to identify barriers and opportunities to increasing the visitation and participation of newand diverse audiences in national parks. Results from this phase of research have lead to the development of a theory of changemodel identifying key ingredients for successful engagement of diverse audiences. This study builds on the results from theexploratory phase and uses site level data from Santa Monica Mountains National Recreation Area to test and validate the model.Four programs designed to engage communities of color, particularly youth, were studied in order to better understand the connections between program inputs, processes, and outcomes and how they lead to program success.