I first saw this film in the theater way back in the 40s when I was a kid and always remembered the ending. There is nothing like the first impression but some movies are always a treat each time they are viewed. Something just resonates with them. This is one of those films and I agree with another reviewer who said Fritz Lang should have directed more westerns. To add to it I have always liked Randolph Scott and Robert Young. In fact, Robert Young stars in what I consider my favorite movie if I have to name just one, not an easy thing to do. That film is Northwest Passage. It led me to the superb historical novels of Kenneth Roberts. Western Union likewise led me to reading Zane Grey's novel which, in this case turned out to be one of those rare cases where I like the movie better than the novel. Not that Grey's novel is a bad one; I just like the movie story better. The movie in no way resembles the novel. It is a completely different tale, one of the biggest departures from a book I have seen.
I can't add much to the other reviews except to say I agree with many of them. I, too, wish it would be released on DVD. "Whatever happened to Randolph Scott happened to the best of me."