Factual error: In the saloon at night, Ben Wheeler says, "I can't afford another Workers Comp claim". Workers compensation wasn't started in the United States until 1902. (00:10:25)
Continuity mistake: In the scene where the wagon train is waiting for Wagonmaster Harlow to decide which fork in the road to take, all the shadows are to the left. As they approach Harlow, the shadows are in front and moment later when the wagons move off the shadows are to the right. (00:26:20)
Factual error: In the final showdown between Julian and Slade, Julian fires a single warning shot, to Slade's belly. Then when Slade draws on him, Julian turns and fires 12 rounds. That's a total of 13 shots from a pair of six shooters.
Answer: It appears to be a woman standing up and reaching for something in her wagon. As the camera pans away, this stool can be seen thrown and landing - breaking apart.