The Protohistoric period in the Pimería Alta marks the transition from prehistory to history, when the social identities among and between historically documented ethnic groups were shaped and negotiated. This period was characterized by social upheaval and demographic change, marked by the transformation of large archaeological complexes after A.D. 1450, the reorganization of the Southwest demographic landscape during the sixteenth century, and the slow yet inexorable encroachment of Spanish colonialism during the seventeenth century. While the Protohistoric period is central to our understanding of culture change and the negotiation of social identity, this period is not well understood from an anthropological perspective, which obscures our understanding of the relationships among and between archaeological cultures and historically documented ethnic groups. Following a reanalysis of archaeological data, written accounts, oral histories, and ethnographic observations, three models of protohistoric demographic change were evaluated within an ethnohistorical framework. Existing data suggest that historically documented ethnic groups have antecedents in multiple archaeological traditions, rather than a single group. Furthermore, inconsistencies in extant archaeological typologies were identified, resulting in a reevaluation of the validity of the use of these typologies as markers of cultural affiliation. An attribute analysis of these typologies reveals that they are not well defined and cannot be reliably associated with a single ethnic group. This analysis demonstrates that there is rarely a one-to-one correlation between an artifact type and an ethnic identity; rather, it is necessary to examine the practices and behaviors that produce materiality and shape residential spaces to understand the suite of practices that construct and/or express ethnic identity.