Henry Darger is a famous outsider artist who lived in Chicago until 1973. He was reclusive at best, and composed a 15,145 page manuscript with illustration of an epic tale called the Realms of the Unreal. With no formal training, his illustrations speak to a more youthful understanding of the world, and though disturbing at times, much like his life and story, they I think resonate with many different viewers. They were composed by tracing, collage, and varied inks and paints, sometimes on both sides of the paper, and illustrate his whole talk about some sisters who are fighting bad people. The enemies of the sisters want to enslave all children and torture them, so it is up to the sisters and the allies to fight for freedom.
There is a documentary I watched about him "In the Realms of the Unreal" that is very interesting and insightful about his life.