Factual error: Though extremely modest by today's standards, the dress worn by Clara at the hoedown shows far too much cleavage for the time. No schoolteacher would ever wear a dress like that in the 1880s.
Factual error: The Henry Repeating Rifle seen in 1865 is impossible, because it's the "King's Patent Henry Rifle" which wasn't out until 1866. The original Henry had a loading tube under the barrel, not one on the side of the breech. Plus the ammo used is the larger, more modern rounds.