According to Maureen O'Hara in her autobiography, "Tis Herself", some stunt men died during the shooting of the film when they fell from their horses during a scene in the middle of a muddy river. Their bodies were allegedly never recovered.
John Ford was especially irritated when producer Herbert J. Yates showed up on location with fellow Republic executive Rudy Ralston. Pointing out the time (it was ten in the morning), Yates asked when Ford intended to start shooting; "Just as soon as you get the hell off my set", Ford supposedly replied. The director later played a practical joke on the two producers at dinnertime. He hired one of his actors, Alberto Morin, to masquerade as a French waiter with poor English skills. During their meal, Morin managed to spill soup on the men, break several plates, and create a general ruckus in the dining room but Yates and Ralston never seemed to catch on to the joke.
Of all the shooting locations listed, none are near or on the Rio Grande. It flows only in Colorado, New Mexico & Texas.
One of the songs performed in this film, "Aha San Antone" was composed by actress, singer and songwriter Dale Evans, who was the wife of singer and actor Roy Rogers. He was at one time lead singer with the Sons of the Pioneers who played the Regimental Singers in this film. Both actors had previously teamed with the Duke in two Republic Pictures westerns. Evans had a small part in "War of the Wildcats (In Old Oklahoma)" in 1943, and Rogers was one of the leads in "Dark Command" in 1940. In addition, the Pioneers sang most of the songs in John Ford's "Wagon Master" earlier in 1950 as well as the theme song for Ford & Wayne's "The Searchers" in 1956 (and even having a brief uncredited appearance during the wedding scene in the later).