The US health system faces mounting pressure to improve population health. Research suggests a need for greater coordination and alignment across the sectors that deliver medical, public health, and social services. This study uses sixteen years of data from a large cohort of US communities to measure the extent and nature of multisector contributions to population health activities and how these contributions affect community mortality rates. The results show that deaths due to cardiovascular disease, diabetes, and influenza decline significantly over time among communities that expand multisector networks supporting population health activities. The findings imply that incentives and infrastructure supporting multisector population health activities may help close geographic and socioeconomic disparities in population health.