Why are some civic associations more effective at advancing their public agendas, engaging members, and developing leaders?  We introduce a multi-dimensional framework for analyzing the comparative effectiveness of member-based civic associations in terms of public influence, member engagement, and leader development.  Theoretical expectations in organization studies, sociology, political science, and industrial relations hold that organizations benefiting from either a favorable environment or abundant resources will be most effective.  Using systematic data on the Sierra Clubs 400 local organizations, we assess these factors alongside an alternative approach focusing on the role of leaders, how they work together, and the activities they carry out to build capacity and conduct programs.  While we find modest support for the importance of an organizations available resources and external environment, we find strong evidence for each of our three outcomes supporting our claim that effectiveness in civic associations depends to a large degree on internal organizational practices.