Diversity’s effect on violence is ambiguous. Some studies find that diverse areas experience more violence; others find the opposite. Yet conflict displaces and intimidates people, creating measurement challenges. We propose a novel indicator of diversity that circumvents these problems: the location of physical structures at disaggregated geographical levels. We introduce this solution in the context of the Troubles in Northern Ireland. Our data reveal a curvilinear relationship between diversity and conflict-related deaths, with the steepest increase at low diversity, driven by an increase in violence when our proxy for the Catholic proportion of the population rises from 0 to 20 percent. These patterns are consistent with a theory of group threat through exposure.