Stuart N. Lake's book on Earp, which the screen credits call a novel, consists of four articles that were originally published in The Saturday Evening Post: "Buffalo Hunters" (25 Oct 1930); "Guns and Gunfighters" (1 Nov 1930); "Tales of the Kansas Cow Towns" (8 Nov 1930); and "The Frontier Marshal" (15 Nov 1930). According to Var, "the hero's name is changed [in the film from Wyatt Earp] to Michael Wyatt, to fend the suits which follow the production of a pseudo-historical play." According to information in the Twentieth Century-Fox Records of the Legal Department at the UCLA Theater Arts Library, in 1929, the year that Wyatt Earp died, Lake, Earp, and Earp's wife had agreed in a contract to equally divide any royalties from the motion picture rights to Lake's work. Also, according to the legal records, Earp's widow approved the contract between Lake and Fox, dated 7 Oct 1932, which gave Fox the motion picture rights concerning Lake's work. Included in the legal records is a letter from Lake in 1939, before production began on Twentieth Century-Fox's remake of this film, in which Lake states that when he sold the rights to his work to Fox in 1932, "it was definitely promised to me, orally, that I was to be employed on the adaptation and screenplay. (I still have all the publicity and year-books announcing the story as a starring vehicle for Warner Baxter.) They sent for me a half-dozen times to come up and talk over things. Bob Yost, Dudley Nichols and Lamar Trotti were all in on some of the huddles, and it was understood that I was to go to work -- verbally. I had two or three long talks with Sol Wurtzel about the thing....Then, to my amazed disappointment, Wyatt Earp was thrown as a sop to Sol Lesser and George O'Brien, a picture turned out for $120,000 and I was left out of pocket and time. They even asked me to come up and talk to the Lesser-O'Brien writers, which I did, but from the first day I talked with Wurtzel, I had sense enough not to tell him, or his help, all that I knew [about Earp]." It has not been confirmed that Yost, Trotti or Lesser were ever involved with this film, or that it was originally intended as a starring vehicle for Baxter.
       Some character names in the onscreen credits differ from those given in the film's dialogue: the character played by George E. Stone is called "David Ruskin" throughout the film, but is listed as "Abe Ruskin"; that played by Berton Churchill is called "Ben Melton" in the film, but is listed as "Hiram Melton"; and that played by Frank Conroy is called "George Reid," yet is listed as "Oscar Reid." Many of the reviews commented on the similarity of Ruth Gillette's portrayal to Mae West; NYT noted that Gillette "has the audacity to use some of Mae West's lines from She Done Him Wrong." Other films based on the same source include the 1939 Twentieth Century-Fox film of the same name, starring Randolph Scott and directed by Allan Dwan (see below); the 1946 Twentieth Century-Fox release of a Samuel G. Engel production entitled My Darling Clementine, starring Henry Fonda and directed by John Ford; and a 1953 Twentieth Century-Fox release of an Andre Hakim production entitled Powder River, starring Rory Calhoun and directed by Louis King. The 1993 film Tombstone, directed by George P. Cosmatos starred Kurt Russell as Wyatt Earp and Val Kilmer as Doc Holliday. In 1994, Lawrence Kasdan directed the film Wyatt Earp, starring Kevin Costner as Earp.