Character mistake: Stoddard in class says the founding document of the country can be added to with amendments. Pompey says it is the constitution written by Thomas Jefferson. Stoddard says 'declaration of independence'. Pompey was right, Stoddard incorrectly corrected him. It IS the constitution. The declaration can't be added to with amendments.
Continuity mistake: At the very beginning of the movie, we see a train rolling down the hill, the first wagon has a dark door in the middle. In the next shot, we see the train coming in the station and the first wagon does not have a door on the middle part of it, but at the beginning of the wagon. Obviously another shot, another train.
Continuity mistake: Toward the end of the movie in the meeting hall, all the good guys are seated on the left and the bad guys are on the right, when looking from the stage. After John Wayne has his talk with James Stewart outside the meeting hall the doors kick open for Stewart to go back to the meeting. The good guys and bad guys in the audience are now on opposite sides of the meeting hall as you look toward the stage from the rear.