We draw on the historiographical concepts of "generational units" and "collective memories" as a framework for understanding the emergence of entrepreneurially oriented cohesive groups within regions. Generational units are localized subgroups within generations that have a self-referential, reflexive quality, by virtue of the members' sense of their own connections to each other and the events that define them. Collective memories are shared accounts of the past shaped by historical events that mold individuals' perceptions. The two concepts provide a valuable point of departure for incorporating historical concepts into the study of entrepreneurial dynamics and offer a framework for understanding how entrepreneurs' historically situated experiences affect them. Our framework breaks new theoretical ground in several ways. First, we synthesize disparate literatures on generational units, collective memory, and organizational imprinting. Second, we specify mechanisms through which imprinting occurs and persists over time. We develop analytical arguments framed by sociological and historiographical theories, focusing on the conditions under which meaningful generational units of entrepreneurs may emerge and benefit from leadership and legacy building, technologies of memory, and institutional support that increases the likelihood of their persistence.