Zooarchaeological deposits present a unique insight into the trajectory of faunal communities through time. Freshwater mussels (Bivalvia: Unionidae) are one of the world's most imperiled faunal groups, and, at the same time, constitute a significant component of the archaeological record in North America. Current conservation efforts can be informed by studies of prehistoric mussel assemblages that catalog communities as they existed prior to any extensive modern impacts, ultimately representing an ecological baseline against which current populations can be evaluated. Over 47,000 freshwater mussel valves were recovered from the late prehistoric (ca. A.D. 700–1200) Kinlock site (22SU526), in Sunflower County, MS. Analyses revealed that the Sunflower River once supported a mussel community with greater taxonomic richness and more evenness among all the major species than today. Additionally, the presence in the archaeological record of numerous species which are currently considered rare, endangered, or extinct in the Sunflower River is indicative of a habitat disturbed by increased human environmental impact in historic times.