Research on language endangerment and revitalization suggests that in many communities, even token uses of endangered heritage languages serve important semiotic functions. This paper proposes that semiotic processes allowing language, and particular uses of language, to serve as indices of identity rely on intertextual relationships to past linguistic usages and to sociocultural knowledge surrounding those past uses. A focus on the use of endangered Native California languages shows how situations of language endangerment have an effect on intertextual processes underlying semiotic uses of language in identity performance. Sometimes, the shared history tying communities whose heritage languages are endangered together serves as an additional resource in developing intertextual relationships which can then be used when heritage languages are deployed semiotically in identity performance. Alternatively, there are times when the disruption of knowledge transmission creates gaps in intertextual relations that can be difficult to bridge.