The Christiana Incident offers a snapshot of the U.S. when the country was sorting into states where slavery was upheld and states that had abolished it, and what racist tension looked like at border states in the mid-1850s.
Research:

Behind the Scenes Minis: Art and Theme Parks
21:25

Interview: Leslie Iwerks
39:57

Uffizi: A Painting, A Bombing, A Restoration
37:36