Factual error: When the riders are watching the wagon train, in the background you can see a communication tower with conical speakers.
Factual error: The film begins in 1851 with Wayne leaving a wagon train and heading south. During this trip he meets young Matthew Garth who he then raises. 14 or 15 years pass, making it 1865 or 66, and Wayne has established his ranch. He and all of the characters are armed with Colt Peacemakers, which were not introduced until 1873.