This paper explores the association between social capital and average happiness in the United States. Social capital is measured as a multidimensional concept consisting of social trust and two different indicators of sociability. In order to employ the variation both over time and across states, the data are organized in either a panel of nine US Census regions over the period 19831998 or in averages over this period in a cross-section of 48 states. The results show that social trust is positively associated with happiness while the potential effects of informal sociability at the level of society only appear significant in the regional estimates. The findings document the importance of social trust for average happiness but also hold more general implications for social capital theory.