Took three days but here's either the first/second Magical Girl ever brought to anime/manga: Himitsu no Akko-chan. Technically the first Magical Girl in manga but the 2nd to have an anime, right after Sally the Witch. I was gonna only do the 1969 version that alot of people probably are aware of but for the sake of Obscuretober, I'm including at least all four incarnations of Akko-chan. From 1962 to 1998.
I don't know much of this series other than the premise is about a girl with a magic mirror that gives her the ability to turn into anyone or anything. It's very hard to find the full series of either timeline online outside of Japan.
And yes as of writing this, I'm aware there's a 2016 manga reboot and a live-action movie but four Akko-chans is my limit.