Someone came by searching for “homicide rate 1940’s.”
Assuming the search was for the United States homicide rates, the chart below covers 1885 to 1950. Homicide rates from 1960 to 215 are at this link.
The caption on the chart below is slightly misleading, in that it says it covers 185 to to 1960. And then we discovered that including 1960 made an odd number of columns. Hopefully, if patience does not run out we will redo the chart back 1883.
For an easy comparison here is a chart showing the United States homicide rate from 1880 to 2015: