Rio Grande was the last of Ford's 7th Cavalry trilogy after Fort Apache (1948) and She Wore a Yellow Ribbon (1949). Although there is still the patriotic, Indian-killing content which is hard to take and the film is a tad too long, it is more emotionally substantial than its immediate precursor, having less concern with the antics of fort life (there is very little of the fort other than the gate) and more with the legacy of the Civil War, here particularly displayed through the relationship between Colonel Kirby Yorke (John Wayne) and his estranged wife Kathleen (Maureen O'Hara) who has come to the fort to bring home their father-deprived son (Claude Jarman Jr).
The usual themes of being-a-man-and-doing-your-duty are central but softened thanks to the contribution of Yorke’s wife who unlike the dutifully self-sacrificing women or wide-eyed young things of the previous two films, expresses a critical point of view which she communicates to both husband and son in scenes of telling poignancy. A radiant O'Hara is wonderful in the role, combining both quiet strength and striking beauty, a combination that Wayne’s Yorke responds to with manly grace, of course (Ford re-combined Wayne and O'Hara for The Quiet Man, 1952).
Ford’s regular players Victor McLaglen, Ben Johnson and Harry Carey Jr. provide the light relief whilst the film has an unusual number of songs, all written by Stan Jones and Dale Evans, "I'll Take You Home Again, Kathleen", "My Gal Is Purple", "Yellow Stripes", "Footsore Cavalry" and performed by a group of singers call the Sons of the Pioneers, here looking decidedly out-of-place in their cavalry blues.