Factual error: The Union Soldiers use a Gatling gun to attack the bushwhackers near the beginning of the film. The Gatling gun was developed, but never used in combat during the Civil War, especially not in the less important Trans-Mississippi theater. Furthermore the Gatling gun shown has 10-12 barrels, the first one developed only had 6.
Great sites
Mistakes
After Zee gets up from the bed and the doctor comes into the room he closes the door, but when they show the doctor again the door behind him is open. See more...
American Outlaws mistakes
Continuity: When Jesse and Frank are telling the doctor that his son was killed (right in the beginning of the movie) Jesse gained a lot of beard growth in five minutes. When they are outside talking to Zee, he has just a light beard, and then when they go inside he has a heavier one.
Continuity: After they capture Jesse James and they take him to the train and gets in he has lot of stubble, but when he says: "yeah you" his face is shaved. Then again when he finally gets off the train and wants to kill Timothy Dalton he has stubble.