Bowman Gum, formerly Gum Inc., had produced the 'Play Ball' sets from 1939 to 1941. No further sports trading card sets were produced until 1948 because resources such as paper as well as the factories were needed for the war effort. When Bowman resumed printing cards they did so with national sets in three sports ushering in the modern era of trading cards. The following is a list with brief summary of Bowman trading card products for the 1940s.