The Challenger Comic from 1946 deals with race, pro-union, pro co-op, and still has a message for today sadly. The caracters in the stories are integrated, different colors work and play together. Something main stream media wouldn't depict for quite some time.
Another amazing old comic (1949) Young Romance # 60, deals with housing discrimination against Jews. This one is drawn by Jack Kirby, who was Jewish and so had personal experience with the attitudes in the story. Powerful stuff.