Earthquakes ravaged the eighteenth-century Bourbon kingdoms of Naples and Guatemala, destroying cities and spurring ambitious programs of scientific investigation and environmental engineering. Though an interrelated technocratic class of architects, engineers, and officials produced the resulting reports, memoranda, and correspondence that documented efforts at aseismic urban design, these sources nonetheless reveal the indispensability of local seismic experts to the Bourbons’ achievement of their post-disaster governing agendas. Guides, informants, and artisans native to zones of high seismicity were foundational to earthquakes’ constitution as scientific objects and cities’ adoption of adaptive, earthquakes-resistant technologies. While extant studies principally frame disasters as times of sociopolitical upheaval, I instead examine catastrophic earthquakes as spaces of scientific inquiry and technological intervention. This analytical shift allows me to argue that colonial cities, rather than epitomizing imperial power, in fact betray empire’s dependence on local environmental knowledge and constructive praxes for its endurance as an urban phenomenon.