In this paper we link unique data on local social infrastructure expenditure with micro-level individual survey data of self-reported social capital measures of trust and participation in community activities. We use both probit and tobit models to estimate the impact of social infrastructure expenditure on social capital formation. Our results imply that the links between social capital, demographic characteristics, human capital, geography and public social infrastructure investment are rather more subtle and complex than much of the literature implies. While we find evidence in support of many of the hypothesized relationships discussed in the social capital literature, our results also suggest that the impact of public social infrastructure investment is affected by both selection effects and free rider processes.