The Gun Violence Archive (a non profit that tallies gun related violence in the United States) defines Mass Shooting as firearm violence resulting in at least four people being shot at roughly the same time and location, excluding the perpetrator.
Using this definition, between January 1, 2019 and November 8, 2019, there have been a total of 359 mass shootings in the United States. 188 of these incidents (i.e. 52%) ended up with 1 or more people dead. So far, 405 people have died and 1,450 people have been injured from mass shooting incidents. Undoubtedly, a significant number of Americans lose their lives to Mass Shootings yearly.
See the map above for the number of fatalities by state, also interact with the map to see the number of injured people and the number of incidents by state.