This master’s thesis presents language community information, a descriptive grammatical sketch and analysis of structures in maqlaqsyals (Klamath-Modoc), a severely endangered isolate language traditionally spoken in present-day southern Oregon and northern California. The basis for this thesis is data from descriptive grammars from Gatschet (1890) and Barker (1964) as well as further linguistic and academic literature surrounding maqlaqsyals. This thesis is important because there is limited literature on maqlaqsyals that is accessible to the language community and this thesis fills the literature gap. This thesis is an example in practice of linguistic sovereignty. This thesis provides accessible linguistic resources written by an Indigenous community member asserting local control. Additionally, this thesis is crucial because children are on longer learning maqlaqsyals as a first language. Second language speakers must become more knowledgeable of language structure in order to converse with other speakers, setting a future environment in which children can be taught maqlaqsyals as a first language.