Objectives. We explored the association between the legal infrastructure of local public health, as expressed in the exercise of local fiscal and legislative authority, and local population health outcomes. Methods. Our unit of analysis was public health jurisdictions with at least 100 000 residents. The dependent variable was jurisdiction premature mortality rates obtained from the Mobilize Action Toward Community Health (MATCH) database. Our primary independent variables represented local public health's legal infrastructure: home rule status, board of health power, county government structure, and type of public health delivery system. Several control variables were included. We used a regression model to test the relationship between the varieties of local public health legal infrastructure identified and population health status. Results. The analyses suggested that public health legal infrastructure, particularly reformed county government, had a significant effect on population health status as a mediator of social determinants of health. Conclusions. Because states shape the legal infrastructure of local public health through power-sharing arrangements, our findings suggested recommendations for state legislation that positions local public health systems for optimal impact. Much more research is needed to elucidate the complex relationships among law, social capital, and population health status. (Am J Public Health. 2012;102:1936-1941. doi:10.2105/AJPH.2012.300656)