The last prehistoric cultures to inhabit the Middle Ohio Valley (ca. A.D. 1000-1650) are referred to as Fort Ancient societies, which exhibited a wide variety of Mississippian period characteristics. What is less well known and little understood are the social processes by which Mississippian characteristics spread to Fort Ancient communities. Through a comprehensive study of SunWatch, one of the few thoroughly excavated Fort Ancient settlements, the author focuses on the development of village social structure within a broad geographic and temporal framework, recognizing border areas as particularly dynamic contexts of social change. As a fundamental study of social patterning of Fort Ancient villages, this work reveals the interrelationships of small social units in culture change and social structure development and provides a full reconsideration of the Mississippian dimensions of Fort Ancient societies and a model for future investigations of larger patterning in the late prehistory of the region.