Continuity mistake: In the scene where John Wayne picks up the red box of money he lifts it onto his back and walks to an open door. As he goes out the door the camera moves to outside and we see John Wayne come out of the building. Now the red box is completely on his shoulder, rather than his back.
Factual error: When the trappers first encounter the Rickarees, the bow cannon is discharged, creating an explosion near the Indians, who promptly turn and ride away. Immediately after, a second shell explodes near them. It would be impossible for a single gunner to sponge out and reload with cartridge and ball in the space of 10 seconds.