Factual error: Disc 2: There is a scene where a cannon shell explodes inside a hospital ward. Everyone in the ward is killed, but there are no signs of limbs torn off or even shrapnel wounds, only some blood here and there. The same thing happens at the Battle of Bull Run when the old woman gets blown out of her bedroom by cannon fire.
Factual error: When John meets a group of escaped slaves in the swamp, he gives them a newspaper clipping about the Emancipation Proclamation. The leader of the group calls it a message from "The White House." From the time it was built until President Theodore Roosevelt, the president's residence was known at "The Executive Mansion." It was President Roosevelt who changed the name to "The White House."