The neighborhood commons, and dog parks in particular, provide a good laboratory to explore the drivers of voluntarism and trust, as well as the situational and demographic correlates that promote or inhibit voluntarism. This analysis connects a central theme of Ostrom’s work on institutions for overcoming social dilemmas to the literature on voluntary actions and the health of small communities. Survey results from more than 500 users of 14 dog parks in the Atlanta area are examined to understand how variation in park and user characteristics predict variation in individual contributions to the commons, including pro-social attitudes and behavior and dispute resolution behavior. Our analysis shows how institutions foster community commons, which are correlated with both voluntarism and the voluntary enforcement of norms on users. These results from a study in the field contribute to a growing literature that explores the circumstances for successful voluntary supply and maintenance of public goods.