Based on a three-year ethnographic case study, this paper examines the processes via which a group of learners at a Pennsylvania college got recognized as speakers of Lenape, an endangered language indigenous to the eastern United States. Using a communities of practice framework, it explores how language acquisition was eased and how community members' identities were negotiated and opposed via authentication processes. A community of practice view provides a handy framework for grasping how this effective learning community operated, and for distinguishing factors that may serve other language revitalization enterprises.