Using a definition of mass shootings similar to the one Congress uses, 34 states and the District of Columbia had at least one mass shooting between 1980 and 2020. California and Florida had the most, with 18 and 12 respectively – though per capita, mass shootings in those states were less common than in D.C., Nevada and Wisconsin, among others. Three states – Texas, Washington and Colorado – had between six and 10 mass shootings. Seven states had three, four or five mass shootings over the 40-year study period. Twenty-two states and the District of Columbia had one or two mass shootings. The remaining 16 had none.