Early investments in state capacity promote persistently higher levels of social capital.

Social capital has been shown to positively influence a multitude of economic, political, and social outcomes. Yet the factors that affect long-run social capital formation remain poorly understood. Recent evidence suggests that early state formation, especially investments in state capacity, are positively associated with higher levels of contemporary social capital and other prosocial attitudes. The channels by which early state capacity leads to greater social capital over time are even less understood. We contribute to both questions using the spatial and temporal expansion of the US postal network during the 19th century. We first show that county-level variation in post office density is highly correlated with a bevy of historical and contemporary indicators of social capital (e.g., associational memberships, civic participation, health, and crime). This finding holds even when controlling for historical measures of development and contemporary measures of income, inequality, poverty, education, and race. Second, we provide evidence of an informational mechanism by which this early investment in infrastructural capacity affected long-run social capital formation. Namely, we demonstrate that the expansion of the postal network in the 19th century strongly predicts the historical and contemporary location of local newspapers, which were the primary mode of impersonal information transmission during this period. Our evidence sheds light on the role of the state in both the origins of social capital and the channels by which it persists. Our findings also suggest that the consequences of the ongoing decline in local newspapers will negatively affect social capital.