The Sam Elliott character tells the immigrants they are fools for having oxen for their train rather than horses. The truth is that most pioneers used oxen rather than horses for pulling their wagons west, unlike the depiction in most westerns. Oxen are slower but better suited for such a trip because they are stronger, able to endure under duress, are less picky eaters, are more sure-footed, can better pull fully loaded wagons up mountains, are less easily spooked, and, upon arrival at a destination, would be better suited to farm life.
James Dutton's rifle, the single-shot Winchester 1885 "High Wall," was the first commercially produced firearm of famous gun designer John Moses Browning, and his first collaboration with the Winchester Repeating Arms Company. Browning would go on to design numerous firearms and patents still in use, including the Winchester 1894 .30-30 lever action rifle, the M2 "Ma Duece" .50 caliber machine gun, and the Model 1911 automatic pistol.
Shea Brennan (actor Sam Elliot) forces the immigrant husband and wife to leave town because they have smallpox. He tells them they are going to die. In reality, he's overstating it a bit. While smallpox is deadly, it's more deadly to children than to adults. Overall, it has a survival rate of about 70%, although survivors often have scarring and/or blindness. Presidents Lincoln and Washington suffered from smallpox when they were younger and recovered. Even so, the fact that his wife and daughter died of it would certainly affect his perspective.
In the opening scene Elsa Dutton (Isabel May) incorrectly states the term "Great American Desert" was coined by professors who were safely far away. The description of the Midwest region of the United States (Nebraska Territory, including Kansas, Oklahoma, and the Dakotas, was made by explorer Zebulon Pike in the early 1800s when he traveled and mapped the area after the Louisiana Purchase in 1803 and the area became part of the United States of America.
LaMonica Garrett's character is likely based on Bass Reeves (July 1838 - January 12, 1910), who was an American law enforcement official, historically noted as the first black deputy U.S. marshal west of the Mississippi River. He worked mostly in Arkansas and the Oklahoma Territory.