"Why was Guy so completely forgotten?" The man she worked for in France, Leon Gaumont, was an inventor and valued invention exclusively. The films Guy directed were used to sell equipment. Documentation attributing direction is scarce before 1905. Film histories written from the 1920s through the 70s would not, of course, catalog her accomplishments. Until 1912 there was no copyright protection for film scripts.
Guy-Blache was integral in the birth of film in France, as well as the development of cinematic narrative. She developed location shooting, she pioneered a studio system years before the same was done by Ince in the U.S. She trained other directors who would go on to earn fame, as well as set designers who are in the history of film. She trained her husband who directed Buster Keaton, which made Keaton a star. She made over 100 synchronized sound films when synchronized sound was still a misty vision.
This book begins the discussion, and perhaps will encourage the work to find and document the work of other women artists.
McMahan's work in piecing together a filmography of the extant films of Alice Guy Blache is exemplary, and hopefully a bellwether for further study.