Paleomobility has been a key element in the study of the expansion of ancient states and empires, including the Tiwanaku polity of the South Central Andes (AD 500–1000). We present radiogenic strontium and oxygen isotope data from human burials from three cemeteries in the Tiwanaku-affiliated Middle Horizon archaeological site complex of Rio Muerto in the Moquegua Valley of southern Peru. At Rio Muerto, archaeological human enamel and bone values range from 87Sr/86Sr = 0.70657–0.72018, with a mean of 87Sr/86Sr = 0.70804 ± 0.00207 (1σ, n = 55). For the subset of samples analyzed for oxygen isotope values (n = 48), the data ranges from δ18Ocarbonate(VSMOW) = +18.1 to +27.0‰. When contextualized with other lines of archaeological evidence, we interpret these data as evidence for an archaeological population in which the majority of individuals had “local” origins, and were likely second-generation, or more, immigrants from the Tiwanaku heartland in the altiplano. Based on detailed life history data, we argue a smaller number of individuals came at different ages from various regions within the Tiwanaku polity. We consider whether these individuals with isotopic values consistent with “nonlocal” geographic origins could represent first-generation migrants, marriage exchange partners, or occupationally mobile herders, traders or other travelers. By combining isotopic life history studies with mortuary treatment data, we use a person-centered migration history approach to state integration and expansion. Isotopic analyses of paleomobility at the Rio Muerto site complex contribute to the role of diversity in ancient states by demonstrating the range of geographic origins rather than simply colonists from the Lake Titicaca Basin. Am J Phys Anthropol 155:405–421, 2014. © 2014 Wiley Periodicals, Inc.