Factual errors: In a scene after the Earthquake, the driver of a Salvation Army wagon tells Blackie Norton that he is heading to "Daly City to get milk for the kiddies." In fact, Daly City was not incorporated until 1911 (five years after the quake). The area did contain dairy farms (owned by John Daly), but was known as Vista Grande.
Revealing mistakes: As Blackie walks away from a building being blown up (actually a process shot), Clark Gable's head becomes momentarily transparent.