The United States faces growing public and policy demands to improve health status on a population-wide basis. This session reviews new research from the Robert Wood Johnson Foundation's Systems for Action research program about the implementation of population health activities in communities across the U.S. Using 16 years of data on a national cohort of metropolitan communities, we show that substantial growth has occurred in the array of organizations and sectors that contribute to population health activities, especially in the years following Affordable Care Act implementation. We also show that this growth has not occurred evenly across the U.S., with both policy and institutional forces shaping the magnitude and pace of change. Finally, we discuss preliminary evidence indicating that expansions in population health activities may help to lower income-related disparities in population health.