Superman - 1941 Cartoon Classic 1st and 2nd Short Films

https://archive.org/details/superman_1941
https://archive.org/details/superman_mechanical_monsters
free to stream or download

More information:
https://en.wikipedia.org/wiki/Superman_(1940s_cartoons)
http://io9.gizmodo.com/5963049/you-can-now-watch-the-1940s-fleischer-studios-superman-cartoons-online