Texas Longhorn cattle had been nearly extinct as a breed for about 50 years when this film was made. Only a few dozen animals were available. In the herd scenes most of the cattle are Hereford crosses with the precious Longhorns prominently placed in crucial scenes.
The theme song, "Settle Down" was later adapted by the score's author, Dimitri Tiomkin, and sung by Dean Martin and Ricky Nelson under the title "My Rifle, My Pony and Me" in Rio Bravo, another John Wayne western directed by Howard Hawks.
There was some concern that John Wayne and Montgomery Clift would not get along since they were diametrically opposed on all political issues, and both were outspoken on their views. According to legend they agreed not to discuss politics and the shooting went smoothly. However both Wayne and Walter Brennan would not get along with Clift, and they stayed away from the young actor when not filming. . Clift later turned down Dean Martin's role in Rio Bravo because he did not want to be reunited with those two actors.
In a 1974 interview, Howard Hawks said that he originally offered the role of Thomas Dunson to Gary Cooper but he had declined it because he didn't believe the ruthless nature of Dunson's character would have suited his screen image.
The role of Tess Millay was intended for Margaret Sheridan but she became pregnant shortly before filming. Instead she suggested her friend Joanne Dru for the role.
During production, many members of the cast and crew caught illnesses and injuries. Howard Hawks was hospitalized for several days after being stung by a centipede. John Wayne caught a severe cold. Joanne Dru suffered from influenza.
This is Montgomery Clift's debut film, but because it was shelved for 2 years, the first film the public saw of Clift was The Search, which he was Oscar-nominated for.
Upon completing this movie, Howard Hawks gave John Wayne a belt buckle that featured the Red River D logo (Wayne later wore this as part of his costume in El Dorado). Wayne later returned the favor and gave Hawks a twin buckle.
After seeing John Wayne's performance in Red River, directed by rival director Howard Hawks, John Ford is quoted as saying, "I never knew the big son of a bitch could act."
The famous scene where Montgomery Clift and John Ireland compare their revolvers was allegedly a reference to John Ireland's endowment, it may also be a reference to Clift's homosexuality.
Howard Hawks was distressed by John Ireland's unprofessional and lecherous behavior during filming, which were partially due to the actor's alcoholism. This contributed to Ireland's part, "Cherry Valance", being drastically reduced in the finished film. At one point, Cary Grant was in consideration for the part (he turned it down).
"Lux Radio Theater" broadcast a 60 minute radio adaptation of the movie on March 7, 1949 with John Wayne, Joanne Dru and Walter Brennan reprising their film roles.
Borden Chase's original script has Tess and Matt escort a mortally wounded Dunston across the Red River, where they stand him up long enough to have him die on Texas soil. Chase vigorously objected to Hawks' change but to no avail.