As long-standing keepers of democracy and information stewardship, library professionals are a natural fit for advocating and promoting sustainability within their communities. From seed libraries to Occupy Wall Street libraries, their view of sustainability extends beyond environmental concerns to include community activism, economic development, and social equity. Empowering people, facilitating dialogue, and providing resources for a more resilient future are at the center of librarians’ vital and changing roles. These visionary professionals have powered libraries’ work as outspoken advocates with well-founded initiatives. For a long time, however, there was no cohesive sustainability-focused venue for sharing best practices, collaborating, and contributing to the profession. In 2013, after one year of focused research and promotion, the American Library Association (ALA) approved a new group, the Sustainability Round Table (SustainRT). This article describes how library advocates built SustainRT over the years and gained momentum with a pivotal webinar series. Clear signs of SustainRT’s early success are a testimony to the critical need for a sustainability-related Community of Practice (CoP). The article shows how the steps taken to achieve this national group’s standing can serve as a model for fostering dialogue and collaboration (often through virtual means) that allows for wide participation.