Suicide imposes substantial threats to a community's operation, functioning, and welfare. We propose that social detachment and isolation from community can be a leading risk factor of suicide behaviors. Using a social capital index derived from the principal component analysis, we show that county-level suicide rate in the US from 2005 to 2017 is strongly and significantly correlated with social capital. A one standard deviation improvement in social capital prevents 0.41–0.44 suicide deaths per 100,000 population per year, resulting in an annual benefit of $41.2 to $44.7 per person based on the value of statistical life in 2017 dollars. At the same time, a higher unemployment rate, a larger male-to-female ratio, and a greater proportion of the white population contribute to rising suicides. These findings highlight the joint role of societal factors and personal traits in influencing individual behaviors.