Based on the 26 star flag (1837-1845), the film takes place in the 1840s. Many of the settlers use Springfield Model 1873 "trapdoor" rifles. This was common in Hollywood because the 1873 was based on the 1861 rifled musket, which closed a continuous line of muskets going back to 1795, so it easily could stand in for a muzzle loading musket to the untrained eye.
Based on the 26 star flag (1837-1845), the film takes place in the 1840s. Coleman (John Wayne) carries a Remington New Model Army revolver, patented in 1858 and manufactured in the 1860s.
(at around 1h 23 mins) Motor vehicles are moving in the far distance (top left of frame).