There were totally 62519 tracts from 1950-2017 in America.
From the map, we can find that the middle part of America suffered the most serious tornado tracts —-the red color’s part means they suffered over 18.97 tracts per square mile.
Relatively, the western part of America almost suffered no tornado tract from 1950 to 2017.
The data was collected from Storm Prediction Center which include
data of tornadoes 1950-2016.