On the surface, Robert Altman’s McCabe& Mrs. Miller may sound like your traditional Western film. The title character, John McCabe (Warren Beatty), is a gambler with a mysterious past who comes to town to set up a business, and he partners up with people in the town, including a saloon owner (Sheehan, played by Altman regular Rene Auberjonois), and another person from out of town who says they can help McCabe do better in his business. However, when two other men come into town to try and buy him out, McCabe refuses, and this sets up a showdown with some gunmen, who work for those two men, who come into town looking for McCabe. But this is a Robert Altman film, and Altman never did anything traditional, so McCabe & Mrs. Miller is different from your traditional Western (though, in my opinion, that doesn’t make it any less good).
For one thing, instead of being shot in the wide-open spaces of someplace like Monument Valley (the location of many a John Ford Western), Altman’s film (which he also co-wrote with Brian McKay, based on Edmund Naughton’s novel McCabe) was set in Washington state (though it was shot in British Columbia), and you get all of the familiar weather of the Pacific Northwest, particularly the rain and the snow (the final shoot-out is set in the snow). In tune with the unfamiliar setting, Altman and cinematographer Vilmos Zsigmond (who went on to shoot two other movies for Altman) give this a grainy look, in contrast to the expansive, well-lit look of most Westerns. It also doesn’t sound like other Westerns, thanks not only to Altman’s traditional overlapping dialogue, but also the things people talk about; you get minor characters talking about whether or not to keep their beard, for example. Nor does the score sound like a traditional Western; it’s made up mostly of Leonard Cohen’s songs (“Sisters of Mercy”, “The Stranger Song”, and “Winter Lady”) – though there’s also “Silent Night” and a musical reference to Ford’s The Searchers – that not only fit in with the melancholy tone of the film, but also underscore the characters and story (“Like any other dealer, he was watching for the card/That is so high and wild he’ll never need to deal another”, from “The Stranger Song”, is a good description of McCabe).
For another, McCabe’s “business” is running a brothel – Westerns in the past had women characters who were understood to be prostitutes (like the characters played by Claire Trevor in Stagecoach, or Shelley Winters in Winchester 73), but because of the Production Code, were never named as such – and his other partner, aside from Sheehan, happens to be a woman, Mrs. Miller (Julie Christie), a prostitute herself. Also unusual is Mrs. Miller happens to be the smartest person in the film; not only does she know how to run the women more efficiently than McCabe ever could, but she’s the 
one who knows McCabe’s efforts to stonewall Sears (Michael Murphy) and Hollander (Antony Holland) – representatives of the Harrison Shaughnessy mining corporation that wants to buy him out – will lead to no good end (not that she can do anything about it; she’s an opium addict, and her last scene shows her in an opium daze). You would also expect McCabe & Mrs. Miller to become involved with each other – especially since Beatty and Christie were involved in real life at the time – but though Mrs. Miller does sleep with him, Altman never shows it, and she keeps it strictly a business relationship otherwise, to McCabe’s consternation; as he gripes, “I got poetry in me!”
Finally, there’s McCabe. When he comes into town, people, especially Sheehan, think he’s a gunfighter, and though McCabe doesn’t like to talk about it, there’s proof at the end he does know how to handle a gun. However, McCabe is mostly defined by his gift for gab, though what he’s saying doesn’t always make sense (“If a frog had wings, he wouldn’t bump his ass so much, follow me?”), and that’s a big departure from the usual laconic hero of the traditional Western. Not only that, but as I’ve hopefully made clear, despite his skill as a gambler, his ability to charm people (though he isn’t always successful at that), and his skill as a gunfighter (though that doesn’t save him), McCabe is pretty much a fool. While Beatty, like many actors when they become stars, was careful about his image, he also went further than most in playing with that image, and McCabe, in all the ways that I’ve described, was definitely a departure. Finally, unlike the traditional Western where the good guys win, no one ends up winning – not McCabe, not Mrs. Miller, not the gunmen who come after McCabe at the end (they kill him, but he kills them too), not an affable young cowboy (Keith Carradine, who went on to become an Altman regular) who is a hit with the women at the brothel, but ends up getting killed by one of the gunmen and certainly not Ida (Shelley Duvall), a mail-order bride who, after her husband is killed, is forced to become a prostitute – except the Harrison Shaughnessy corporation. Of course, this is a downer ending, but Altman nevertheless makes it an exhilarating experience to watch. Though Altman and Beatty quarreled during the shooting – both of them were control freaks, and while Beatty liked doing a lot of takes, Altman didn’t – that doesn’t show up on screen. According to Beatty, John Huston called McCabe & Mrs. Miller the best Western he had ever seen, and it’s easy to see why.