I'm pretty sure The Man Who Shot Liberty Valance is on every list of "Movies Guys Should See". Deservedly. I've seen it before, I think as a teenager. When I noticed it was Amazon Prime-available, I put it on.
US Senator Ransom Stoddard (Jimmy Stewart) and his wife Hallie (Vera Miles) are headed back to a small town for the funeral of Tom Doniphon (John Wayne). Everybody's surprised at that, because Tom was a poor nobody. But Stoddard decides to come clean about the events of many years ago… flashback time!
Back to the days when the town was a barely-civilized oasis in an essentially lawless territory. Stoddard is incoming as the town's new lawyer, but the stage he's on is waylaid by a vicious psychopathic trio of villains, let by (guess who) Liberty Valance (Lee Marvin). Stoddard stands up to the thieves when they threaten an old lady, but he's savagely beaten and left for dead.
But he's not dead, and is in fact rescued by Doniphon, taken to town where he makes a semi-miraculous recovery thanks to nursemaiding by a young Hallie.
The problems soon become obvious. The town is successfully terrorized by Valance and his thugs. Stoddard is an idealist, thinking that the rule of law must be brought to the territory. Doniphon is a cynic, scorning Stoddard's pacifism, but (on the other hand) grudgingly respecting him for his bravery. Complicating things quite a bit: Doniphon sees Hallie as his girl, and he's fixin' to propose once he gets his ranch house fixed up. But Hallie is increasingly drawn to Stoddard … It's a neatly choreographed conflict.
A large number of fine supporting actors show up. Andy Devine as the town's cowardly ineffective lawman; Edmond O'Brien as the drunkard editor of the town's newspaper; Woody Strode as Doniphon's buddy/partner; Lee Van Cleef and Strother Martin as Valance's assistant thugs.