In this article we explore the relationship between spatial proximity and indices of social connectivity during the A.D. 1200–1450 interval in the United States (U.S.) Southwest. Using geographic information systems (GIS), we develop indices of spatial proximity based on the terrain-adjusted cost distance between sites in a regional settlement and material cultural database focused on the western U.S. Southwest. We evaluate the hypothesis that social interaction is a function of proximity and that interactions will be most intense among near neighbors. We find that this hypothesis is supported in some instances but that the correlation between proximity and interaction is highly variable in the context of late precontact social upheaval. Furthermore, we show important discrepancies between the Puebloan north and the Hohokam south that help to explain differences in community sustainability in the two regions.