As Briggs loads his wagon on the ferry over the Missouri River -- presumably the Lone Tree Ferry between Omaha, NB and Council Bluffs, IA -- you can see the modern-day river restraining berms along the bank.
After Briggs is rescued by Cuddy, she takes him home on her wagon. As she stops outside Briggs face is dirty at 26m 11s but he is still on the wagon but with a clean face at 26m 23s after a change of shot.
When Mary Bee is at the grave of the little girl and stays behind to "repair it", her bonnet blows away. She doesn't pick it up when she gets on the horse and rides away. However, when we see her hanging, she is wearing her bonnet.
When Cuddy draws the black bean, which means she will transport the women, someone remarks that it is May 4, and she should be back by the 4th of July, which means, of course, that it is late spring. Yet in the first few days they run into snowfall, and Briggs constantly complains about the cold nights. The women show no apparent discomfort when they are bathed naked in a stream.