During the stampede, when the wagon flips, it's obvious Vindicator is no longer tied to the wagon.
In the final fight scene between James Stewart and Brian Keith, there is a close shot of the calf watching from underneath the stairs. However, when they cut to the long shot, the calf is no longer there.
In the opening scene set in St. Louis, Missouri, there are images of the state flag of California, where the film was made, flying in the background. There are also very large hills seen in the background while the area around the real St. Louis is relatively flat.