Patterns of social conflict and cooperation among irrigation communities in southern Arizona from the Classic Hohokam through the Historic period (c. 1150 to c. 1900 CE) are analyzed. Archaeological survey of the Gila River Indian Community has yielded data that allow study of populations within the Hohokam core area (the lower Salt and middle Gila valleys). An etic design approach is adopted that analyzes tasks artifacts were intended to perform. This research is predicated on three hypotheses. It is suggested that (1) projectile point mass and performance exhibit directional change over time, and weight can therefore be used as a proxy for relative age within types, (2) stone points were designed differently for hunting and warfare, and (3) obsidian data can be employed to analyze socioeconomic interactions. This research identifies variation in the distribution of points that provides evidence for aspects of warfare, hunting, and the social mechanisms involved in procuring raw materials. Ethnographic observations and archaeological data suggest that flaked-stone points were designed (1) for hunting ungulates, or (2) for use against people. The distribution of points through time and space consequently provides evidence for conflict, and those aspects of subsistence in which they played a role. Points were commonly made from obsidian, a volcanic glass with properties that allow sources to be identified with precision. Patterns in obsidian procurement can therefore be employed to address socioeconomic interactions. By the 18th century, horticulturalists were present in only a few southern Arizona locations. Irrigation communities were more widely distributed during the Classic Period; the causes of the collapse of these communities and relationships between prehistoric and historic indigenes have been debated for centuries. Data presented here suggest that while changes in material culture occurred, multiple lines of evidence for cultural continuity from the prehistoric to Historic periods are present. The O'Odham creation story suggests that the population fluctuated over time, and archaeological evidence supports this observation. It appears that alterations in cultural practices and migrations occurred during intervals of low population density, and these fluctuations forced changes in political, economic, and social relationships along the middle Gila River.