Advances by nearby innovators – close enough to interact in person – play key roles in patented technology development. Patents frequently cite nearby innovations, identifying these local innovations as the background for further patented inventions. Such citations reveal narrow geographic areas with intensely active innovation communities advancing similar projects and technologies. Local innovators – working within a commutable distance of 40 miles or less of each other – accounted for 25 percent of all patent citations between 2010 and 2019 and about 21 percent of citations by disinterested patent examiners reviewing patent applications. These percentages of citations to local advances are much higher than would be expected were patented technology development distributed randomly across all geographic sources. While local citations do not necessarily indicate that the cited and citing innovators worked together, their co-location indicates that the cited and citing parties were close enough to interact or to have benefitted from shared resources such as local information networks and common pools of skilled workers emerging from nearby universities. Local concentrations of citations identify regions and innovation communities producing many distinctly new advances capable of qualifying for patents. These advances are potentially important in at least two key respects: first, locally concentrated inventions disclosed in patents are important in technology development because they are outlier advances with material differences from predecessors that are capable of significantly shifting the pace and directions of technology development and, second, such locally concentrated advances (and their associated patent rights) can advance local commercial success by enabling highly functional, popular, and profitable products and services. Local concentrations of patent citations identify associated communities of especially capable and active innovators. Local innovators producing large numbers of patented advances are rapidly expanding the outer boundaries of their fields. Where these parties are concentrated in particular regions, the associated communities may establish innovation synergies that enhance innovation processes and diversify innovation results. Their group efforts may pioneer key technologies that would not have emerged from more widely separated innovators. The geographic and technological information embedded in patent records reveal many settings where geographically compact communities of innovators are advancing cutting edge technologies. This article examines innovation hot spots identified from geographic and technological information in approximately eight million citations to United States utility patents issued between 2010 and 2019. These citations, the location of the citing and cited innovators, and the technologies covered by their respective patents indicate that local innovation communities produced many technologically related innovations over this period (particularly in some of our largest innovation centers such as Silicon Valley). Patent applicants and patent examiners cited local patents from less than 40 miles away much more frequently than more distant patents, indicating that technologically similar innovation projects (and successful inventions) were particularly common in local technology hubs. More distant innovations were cited less frequently despite the availability to distant innovators of full descriptions of earlier advances in patents, electronic research services making patents easily available at great distances, and modern means for interacting with distant innovators via electronic communications or travels to meet with distant researchers. Despite electronic resources and other enhanced means to interact with distant innovators, inventors emphasized locally prevalent technologies and built on what they could learn locally. Local proximity – and the potential for direct interactions – was a demonstrably powerful force promoting successful technology development.