Obsidian was the lithic material preferred by the aboriginal inhabitants of southwestern Idaho, but archaeologists and ethnographers have reported that this material was obtained in Yellowstone National Park and central Oregon. Evidence for tool production in the vicinities of the two local sources is minimal, superficially indicating little procurement of these materials. However, x-ray fluorescence analysis of regional sources and archaeological collections demonstrates that, in fact, both sources were exploited over a period of 10,000 years. This study indicates that lithic tool production occurred primarily at the consumer sites rather than at the source areas.