Gender in speculative fiction
The first known female superhero is writer-artist Fletcher Hanks's minor character Fantomah, an ageless, ancient Egyptian woman in the modern day who could transform into a skull-faced creature with superpowers to fight evil; she debuted in 1940 in Fiction Houses "Jungle Comics".
Yankee Girl
The first superheroine called Yankee Girl was Kitty Kelly, created in a seven-page story by an unknown writer and artist in Four Star Publications' "Captain Flight Comics" #8 (cover-dated May 1945). She made subsequent appearances in issue #9 (Sept. 1945), in a story by an unknown writer, penciler Maurice Whitman and inker Ann Brewster, and "Red Seal Comics" #17 (July 1946), from Chesler Publications / Dynamic Publications, in which the feature is called "Kitty Kelly" rather than "Yankee Girl".