The areal frequency of tornadoes in the United States by Counties, 1880–1931

In this third paper of statistical studies of the distribution of tornadoes in our country in the recent half-century, the writers submit the county-distribution map with comments. It shows the results of the study of the distribution based upon smallest available unit. Of course, it is understood that, under the inspiration of Colonel Finley's enthusiasm, the gathering of tornado-data was fairly comprehensive until the middle of the nineteenth century. A hiatus of a score of years then ensued in which tornado-facts were of rather fragmentary nature. But from 1916 on, some 5000 observers were cooperating in collecting fairly complete field-data. Of the 4000 tornadoes studied in this paper, about three-fifths occurred in this later period, and of the balance, the major portion occurred in the earlier period.