I noticed in the Wikipedia article, it says that the movie was set in Monterey, Calif. (where it was filmed), but, when watching Clash by Night recently, I noticed that the local tuna company in the film is depected as The San Xavier Fish Processing Company. Also, there were several references in the film to "Buckman County." Also, there was a reference to Fresno as being "upstate," so fictional San Xavier would have to be somewhere in southern California.