Dean Martin's agent approached Howard Hawks to consider his client for the role of the drunken deputy Dude. Hawks agreed to meet with Martin at 9:30 the next morning. When Hawks learned that Martin had done a show in Las Vegas until midnight, and hired a plane to fly him to the meeting, Hawks was so impressed that he simply sent Martin to get a costume and told him he had the part.
Inside joke: When Chance (John Wayne) wants to deputize Colorado he asks Stumpy (who is off camera) where he keeps the deputies' badges. While Chance is looking for the badges, Stumpy (Walter Brennan) still off camera tells him to look after his own props. Wayne started off in movie as a prop man and was known to get irate if the props were not where they were supposed to be.
On May 8th 1958, just one week into shooting Ricky Nelson celebrated his 18th birthday. As a gift, John Wayne and Dean Martin gave him a 300 lb. sack of steer manure, which they then threw Nelson into as a rite of passage.
Howard Hawks did not want to cast Ricky Nelson, whom he considered to be both too young and too lightweight, and deliberately gave him the fewest possible number of lines for a third-billed star. However, he later admitted that having Nelson's name on the poster had probably added $2 million to the film's box office performance.
John Wayne had deliberately moved away from westerns after The Searchers (1956), but none of his films since then had been particularly successful or well received. This film was a return to the genre for him.
Howard Hawks always wanted someone who would connect with teenagers to play Colorado. Reportedly, his first choice was Elvis Presley, who was enthusiastic about the opportunity. Unfortunately, Presley's manager, Colonel Tom Parker, wanted too much money and top billing. Neither Hawks nor John Wayne would have any of it, so the search continued. Presley joined the US army in March 1958, two months before filming began.
For most of the film Chance (John Wayne) has the front of his hat turned up to make him look a little soft and friendly. However in the tough guy scenes when Chance informs Nathan Burdette that he will have Stumpy kill his brother if there is any trouble, the front of the hat is turned down, in traditional tough guy mode.
After seeing the film, Gary Cooper said it was "so phony, nobody believes in it." Ironically, Cooper had been a visitor to the set since he was filming The Hanging Tree (1959) nearby. "Rio Bravo" is considered to be John Wayne and Howard Hawks' reply to Gary Cooper's own film High Noon (1952) because neither Wayne or Hawks thought a real lawman would want or need to ask for help in handling a problem like Cooper's character did in that film.
John Wayne's working script for the film was auctioned by Heritage Auctions for $20,315 by the Texas-based company. All but last three of its 122 pages were folded in half, a habit that the actor had of doing with all of his working scripts.
The movie had an interesting preview trailer. In the trailer, Ricky Nelson finishes playing his guitar, then he turns to the camera and talks about the exciting nature of the film. After some clips are shown, they cut back to Nelson who lists the cast members. When he does not mention his own name, we hear the voice of Dean Martin say off camera "What about Rick Nelson"?
In an interview Walter Brennan stated that for years after this film was released people who met him for the first time expected him to limp like Stumpy. He said he considered it a tribute to his acting since he had to constantly remember which leg to limp on.
Although Harry Carey Jr. was listed in the credits on-screen, he does not appear in the picture. Carey had a drinking problem at the time. He called director Howard Hawks "Howard" instead of "Mr. Hawks" on one of his first days on the set, infuriating Hawks. His contract, including his pay and his screen credit, was honored, but his part (a townsman) was cut.