Looking at this map, we can see that Illinois, California, and Texas have had the most mass shooting events. Diving further, if you look at all the states that have had more than 100 incidents since 2018, you will see that they all have major cities within them.
This bar graph contains the same data as the map; however, it better illistrates the magnitude in which some states experience more mass shootings than others.
It is no surpise that the states with the most mass shootings (Illinois, California, and Texas), are also the states that have had the most people affected by them.