Since the advent of the National Association in 1871 and continuing on through the just-completed 2020 campaign, the Major Leagues have seen 19,905 players take the field for at least a part of a regulation game. All of them have been men. In 1931, it almost wasn’t so.
Jackie Mitchell was a 17-year-old lefty when the Double-A Chattanooga Lookouts signed the pitcher in Spring Training, 1931. After two New York Yankees reached base to start the game, the Lookouts manager pulled the starter in favor of Mitchell. Mitchell, a female, then struck out Babe Ruth and Lou Gehrig before walking Tony Lazzeri and getting pulled (h/t to the Smithsonian Institute).