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 December 31, 2019, there were a total of 417 mass shootings in the United States. 218 of these incidents (i.e. 52%) ended up with 1 or more people dead. So, unsurprisingly, 464 people died and 1,705 people were injured from mass shooting incidents in 2019. 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.