This article analyzes the historical practices of one intergenerational activist community—squatters in New York City—to ground an ethnographic exploration of how oral history works as an affective social practice and a means for harnessing the authority of history. By comparing three case studies of oral history telling, the research presents instances in which history has been consciously used to try to pass on activist knowledge to a new generation through public discussions about the past and by making intimate conversations about the past into public documents. Oral history, a formalized practice with roots in the academy, thereby makes the power of history accessible to grassroots social movements. Its combination of authority and affective impact make it a powerful history-telling tool.