This research explores how people's relationships with the spirits of the dead are embedded in political histories. It addresses the ways in which certain spirits were integral "inhabitants" of two social environments with disparate political traditions. Using the prehistoric mortuary record, I investigate the spirits and their involvement in socio-political affairs in the Prehispanic American Southeast and Southwest. Foremost, I construct a framework to characterize particular social identities for the spirits. Ancestors are select, potent beings who are capable of wielding considerable agency. Ancestral spirits are generic beings who are infrequently active among the living and who can exercise agency only in specific contexts. Anonymous groups of spirits are collectives who exercise little to no agency. I then examine the performance of mortuary ritual to recognize these social identities in the archaeological record. Multivariate analyses evaluate how particular ritual actions memorialized the dead. They concentrate on treatment of the body, construction of burial features, inclusion of material accompaniments, and the spaces of ritual action. Each analysis characterizes the social memories that ritual acts shaped for the spirits. When possible, I supplement analysis of archaeological data with ethnohistoric and ethnographic information. Finally, I compile the memories to describe the social identities for the spirits of the dead. In this study, I examine the identities surrounding the spirits in both a Mississippian period settlement on the Georgia coast and in several Protohistoric era Zuni towns in the northern Southwest. Results indicate that ancestors were powerful members of political factions in coastal Mississippian communities. In contrast, ancestral spirits and collectives of long-dead were custodians of group histories in Zuni communities. I contend that these different spirits were rooted in political traditions of competition. Mississippian ancestors were influential agents on cultural landscapes filled with contestation over social power. Puebloan ancestral spirits were keepers of histories on landscapes where power relations were masked, and where new kinds of communities were coalescing. This study demonstrates that the spirits of the dead are important to anthropological understandings of socio-political trajectories. The spirits are at the heart of the ways in which history influences and determines politics.