When Call and Gus are watching Bob Allen drive his horses into town, and Gus is talking about fighting him, the pistol barrel that Gus is holding changes from his left to his right hand at the end of the scene.
(at around 1 min) A horse trainer can be see running in front of the lead Ranger's horse as they are being tracked by Kicking Wolf.
When the story starts, in 1858, Elisha Marshall Pease, who is presented as the then Governor of Texas, was no longer in office since December 21, 1857, Hardin Richard Runnels being the actual Governor of Texas instead.