Buster Keaton was one of the great actors and directors of the silent era of Hollywood. His 1926 "The General" is considered one of his masterpieces and tells the true story of the Great Locomotive Chase when Union soldiers during the American Civil War hijacked a train on the Atlanta to Chattanooga line behind enemy lines and did a huge amount of damage to Confederate supply chains.

In the biography of Keaton "Cut to Chase" they mention that the history text Keaton went to for facts to base his script on on was told from the Union perspective but Keaton changed it so the Union were the villains kidnapping the Georgian protagonist's lover and the Confederates are the heroes. The book states that Keaton made this change because movie audiences would not accept Confederate villains and Union heroes, it would be necessary to reverse this to win their audiences. Keaton himself wasn't a Southerner (he was born in Kansas and traveled a lot as a child but spent his summers in Michigan) so it can't have been personal.

Why would this be necessary? More Americans lived in formerly Union states than formerly Confederate states so why would the American film audience of 1926 want Confederate heroes and Union villains?