The Clean Air Act (CAA) utilizes an intergovernment partnership, relying heavily on the states for implementation. However, local governments have emerged in recent years as key players in improving local air quality. With no official role under the CAA and research typically overlooking their efforts, they are serving as "hidden" partners in the implementation process. Nevertheless, they are playing a role in improving and maintaining air quality in some local communities. Analysis of air quality monitoring sites indicates these initiatives can be successful, if the local government has the capacity to effect change across the entire area.