Poor mental health is a concern in the US and world-wide. In this study we examine the effects of socioeconomic and environmental variables on the number of days of poor mental health reported across US counties. The results suggest that educational attainment, employment opportunities including self-employment, and social capital have important benefits in terms of community mental health. Other socio-demographic variables also tend to have predicted effects, as does the amount of sunshine in January, which is our control for Seasonal Affective Disorder. The general conclusion of the study is that living in a non-metro county and adjacent to a metro core, is associated with greater happiness. Mental health days also increase considerably due to natural disasters and they are affected by regional climate variability. For policymakers concerned about reducing the average number of poor mental health days across the nation, our results suggest that reducing poverty is a more powerful strategy than reducing income inequality.