Irving Cummings filled in as director from 14 October 1938 to 24 October 1938, when Henry King was bed-ridden from a swelling in his ear.
A scene in which a horse falls to its death from a cliff, and the subsequent public outcry, led to the American Humane Association (AHA) overseeing filmmaking through its new Film and TV Unit. Eventually they introduced the now-familiar AHA certification, "No animals were harmed in the making of this motion picture."
After the two horses that were blindfolded and forced to go over a cliff were killed, a new rule was enforced and later endorsed by The Humane Society of America in which strict standards were created to protect Animal Actors in which at the end of the movie and added to the credits listed as "No Animals Were Harmed or Injured in the Production of this Film...".Now all films involving any Animal Actors must have present a member representing The Humane Society of America to insure that all animals are treated humanly and given a safe environment in which to work.
In the scene where a wagon and its two horses go over the edge of a 75-foot cliff into the river below, the stuntman driving the wagon wasn't hurt, but the two horses were killed.
The film shows both Jesse and Frank going off the cliff on horseback. In reality the stunt was performed once and shot with two cameras.
While shooting his role in the Ozarks, Lon Chaney Jr. fell off his horse during a chase and was trampled by the horse behind him. He was not injured badly - he managed to finish his scenes that day. But director Henry King, blaming Chaney's nightly drinking for the mishap, fired him, and he was dropped by his studio (20th Century Fox.)