Factual error: The movie begins at the end of the Civil War, 1865; it then moves ahead 7 years, to 1872 in Wyoming. Several characters are wearing gun belts with cartridges on the belt. The pistols are Colt Peacemakers probably .45 cal. The problem is that the gun and cartridge were not introduced until 1873 and would take several years to become commonplace. (00:18:31)
Factual error: When Wyatt (Kevin Costner) becomes the sheriff/deputy/policeman of Wichita, Kansas, you can plainly see mountains in the background - there aren't any around there. (01:04:47)
Factual error: During a shootout at the end of the movie, one of the gunmen with a rifle is wearing a wristwatch. (02:58:30)
Factual error: Throughout the entire film the wrong holsters are used. They are wearing "drop loop" holsters but they weren't invented until the 1930s.
Suggested correction: The claim that "drop loop" holsters weren't invented until the 1930s is incorrect. The style often called the "Mexican Loop" (or Mexican Drop-Loop) holster was already in use by the mid-1870s to early 1880s, especially in the American Southwest and northern Mexico. These rigs were worn over cartridge belts and featured loops that secure the holster to the belt. https://cochiseleather.com/western-gun-leather-history.aspx.
