Factual error: John Blair rides for the pony express, which operated until October, 1861. However, all of the handguns in the movie are cartridge Colts, which did not come into existence until 1871.
Continuity mistake: In the scene where we see Calamity Jane and Wild Bill Hickok leave the town by stagecoach, the horses are all a dark colour, then when we get another shot of them travelling along a roadway one of the horses has changed to a white horse.
keiko
Factual error: This movie takes place post-civil war, and Fisher, in his first discussion with General Cortinas refers to the "Republic of Texas" being ripe for the taking. Texas ceased to be a republic in 1845, when it joined the United States.