The fate of regions and of nations increasingly depends upon ideas and innovations to facilitate growth. In recent years, geographers have made fundamental contributions to our understanding of the innovation process by exploring the diffusion of innovation, the location of R&D, and the geography of high-technology industry. This paper examines the geographic sources of innovation, focusing specifically on the relationship between product innovation and the underlying “technological infrastructure” of particular places. This infrastructure is comprised of agglomerations of firms in related manufacturing industries, geographic concentrations of industrial R&D, concentrations of university R&D, and business-service firms. Once in place, these geographic concentrations of infrastructure enhance the capacity for innovation, as regions come to specialize in particular technologies and industrial sectors. Geography organizes this infrastructure by bringing together the crucial resources and inputs for the innovation process in particular places. Using a direct measure of commercial product innovation, an empirical model of the geography is presented. The model tests the hypothesis that innovation is concentrated in places that possess a well-developed technological infrastructure. The analysis confirms this hypothesis; innovations cluster geographically in areas that contain geographic concentrations of specilized resources indicative of technological infrastructure. The spatial concentration of these resources, furthermore, reinforces their capacity to innovate.