This paper describes ongoing work to develop a corpus of Cahuilla language from the John Peabody Harrington collection, which contains linguistic and ethnographic fieldnotes documenting Indigenous languages of California and other regions across the Americas. Handwritten notes present numerous processing challenges, including scratch-outs, multilingual entries in Spanish and other Indigenous languages, unique abbreviations, and varying script orientations. We compare the efficacy of deep learning text recognition models to convert images of the notes into a machine-readable format, with a focus on respecting tribal data sovereignty in our methods. We find that Pylaia is the most accurate model for our data. Finally, we present the preliminary findings and indicate future directions for developing a Cahuilla corpus.