Dorothy Arzner wasn’t the first female film director in the U.S., but she was really the only one working in the studio system during most of the period that’s known as the Hollywood Golden Age. Her short career was still incredibly prolific.
Research:

Peter Kropotkin's Mutual Aid, Part 1
45:03

SYMHC Classics: Haymarket Riot
37:40

Behind the Scenes Minis: Serving Lip and Ethics
26:19