Preparing to hang Jake and the Suggs brothers, Call orders them to get their boots off and we see Dan stoop to comply, yet when it comes time to hang Jake, Jake spurs his horse before Gus can slap it, and there's a closeup of Jake's spur and boot.
Clara gives Newt a Sorrel horse with a star, but he never is seen riding this horse at the ranch or any other time. He his always riding a light roan with a blaze face.
Just before Deets (Danny Glover) dies from being speared by an Indian, he's shown with his eyes gradually closing to a slit. After a cut away and return to show Deets' face again, his eyes are wide open.
When The Suggs Gang is hanged, they swing and choke to death, instead of breaking their necks. But they die within a couple of seconds when choking to death would take a lot longer to kill them.
After crossing over 80 miles through the "Badlands" without water, the cattle don't start running until the river is in view. In truth, thirsty cattle can smell water for many miles, and would have stampeded towards the water much earlier than depicted in the movie.
Cavalry "Captain" Weaver wears a uniform with the double-breasted three times, three button pattern of a major general. Even if the captain had been wearing a frock coat as he is in the film, it would have been single-breasted without the three separate groupings of buttons.
When the army is trying to take the horse from Dish, the Captain mentions that his horses were tired of chasing Red Cloud. "Red Cloud's War" lasted from 1865 until the signing of the Treaty at Fort Laramie in 1868. In the second episode, Captain McCrea mentions upon leaving the saloon where he beats up the bartender that they would have been remembered if they had been killed by the Comanche's like Custer had by the Sioux. The Battle of the Little Big Horn where Custer was killed was in 1876, eight years after the Treaty of Laramie that concluded Red Cloud's War.
When Woodrow and Gus ride up on the place where the Suggs Gang stole the horses after killing the herders, the buzzards flying above the bodies are fakes.
When Call beats up the Cavalry Scout for hitting Newt, the branding iron that Call uses flexes when he moves it around. It is obviously made of rubber.
During the scene preceding Deets's death, when Newt Dobbs is saying goodbye, a modern dirt road is visible over Dobbs's right shoulder.
While tracking Jake and the horse thieves, when they see the buzzards circling, Gus points up and says something to Call, but there is no audio.
July Johnson enters a room to visit Elmira, who is sick in bed. He closes the door behind him, and the audio is the sound of a door solidly closing shut. But look closely, and you will see that the door did not close shut, but in fact "bounced" open, and remains a few inches ajar with some light coming in from the outside.