Off the main part of town, but still nearby, is a small stone building with a large sign out front denoting "Jim's Journey." It tells the story of Jim, a character in Huck Finn, by Mark Twain, based upon a real person, a black slave at the time he wrote the book.
The building is a small one room place filled with stories, photos, and artifacts relating to the slavery at the time, and the real people it involved. It is self guided. There wasn't even someone there other than myself when I visited.
The story is well told, well laid out. You feel the pain, the frustration, the reality of slavery. I highly recommend stopping here if you are in Hannibal, and just for the record, I am an old white guy, so my perspective is not one viewing it as one who this is all too familiar to. It's important to hear other peoples' histories and stories.