This thesis examines the grammatical aspect markers of an extremely endangered language, Coeur d’Alene. Coeur d’Alene is a Southern Interior Salish language spoken by two remaining fluent speakers in Northern Idaho. The Coeur d’Alene aspect system has not previously been subject to a formal analysis. There are three grammatical aspects in the language, traditionally called the completive (∅), customary (ʔec-) and continuative (ʔic-). In this thesis I reanalyze the completive as a standard perfective, the customary as a general imperfective and the continuative as a progressive. The thesis provides data on the different readings that these grammatical aspects induce on the four Vendlerian verb classes of activities, states, accomplishments and achievements. I adopt the semantics used by Bar-el (2005), who follows the formal model of aspect laid out by Rothstein (2004) to analyze the Squamish language.