The Wari Empire expanded and maintained control over many areas in the Andes for nearly four centuries (600–1000 C.E.). This chapter documents changes in power relations and political institutions on the Wari–Tiwanaku frontier. The settlements of both polities are well documented along their border in the Moquegua Valley of southern Peru where Wari controlled their provincial settlements from the lofty heights of Cerro Baúl. We assess the changing nature of the incorporation of different social groups within the Wari political structure of the frontier province over the course of the Middle Horizon. As Tiwanaku social groups joined the Wari colony, new sets of public expressions of power emerged, both from within these Tiwanaku groups and from the Wari administration itself. By examining artifactual remains and the design of architectural spaces, we elucidate the changing power relations between Wari, their subject populations, and their Tiwanaku neighbors.