Although there are scenes that show huge buffalo herds with what looks like thousands of animals, large buffalo herds didn't exist at the time this film was made (1923). The buffalo had been hunted almost to extinction during the late 19th century, with millions of them being slaughtered, and its numbers hadn't yet increased enough to comprise large herds. Cameraman Karl Brown used small lead castings of various sizes of buffalo, placed the larger ones toward the camera and used diminishing sizes in the background for depth. All the castings were mounted on a series of moving chains, those in the rear moving very slowly while the rows of chains moved increasingly faster as they neared the foreground. The castings were hinged so that they moved with an undulating motion, which made them appear to be actual buffalo running. The chains were placed out of view and the mechanical buffalo were placed in front of a painted background containing distant buffalo. The result was a scene of "thousands" of buffalo, when in reality most of them were basically statues.
To get enough covered wagons for the film, a call went out in California to families that still had their ancestors' covered wagons which had brought them out west--these were gathered so wagons used were authentic, though some had apparently been repaired a bit.
This was the favorite film of Japanese producer Tomoyuki Tanaka, the creator of Godzilla and producer of various films by Akira Kurosawa.
The top-grossing US film of 1923.
In an early cut of this film prior to its release, director James Cruze appeared in a brief cameo heavily disguised as an Indian. Screenwriter Jack Cunningham wrote him a memo saying that, even if viewers didn't recognize him from his days as an actor, he looked too "white" alongside the genuine Indians who appeared in the film. Cunningham prevailed, and the scene was deleted.