This dissertation is concerned with the past tense system in Mvskoke (Creek), an endangered Muskogean language spoken by the Muscogee (Creek) Nation and Seminole Nation of Oklahoma, as well as by the Seminole Tribe of Florida. Mvskoke has four (previously five) past tenses and a speaker's choice between them depends on both i) how far in the past the eventuality took place and ii) whether the speaker learned of that eventuality as it happened. Additionally, three of the past tenses appear on nouns where they either receive interpretations similar to English former or provide a relevant past time from which the NP's referent is known, similar to the English expression that N from this morning. While the past tense system of Mvskoke has been described by numerous sources in the 1800's and 1900's, this dissertation constitutes the most extensive semantic investigation of the tenses.