Factual error: The US Cavalry are careful not to run into Confederate cavalry from Fort Davis, who are shown in the distance. Fort Davis was indeed occupied by the Confederates from 1861 to 1862, but was then abandoned until 1867. The film is set in 1864, so there would be no Confederate troops at Fort Davis.
Factual error: When running through the train yard, all the engines are diesel. The movie is set in the 20's or 30's. Diesels were not in use then, only steam engines.
Factual error: When the race starts, the people are waving American flags with 48 stars: 6 rows of 8 stars each. However, in 1908, when the race took place, there were only 46 states.