According to IMDb, Curse of the Undead (1959) is the first vampire western movie. Depending on your definition, that might also make it the first Weird West movie. (If you can find an example of an even older Weird West movie, let me know!)
Now, personally, I'm not a fan of this era of Westerns. I find the John Ford/John Wayne movies boring. There's just something about 1950s Westerns that pull me out of the movie. For example, I don't like how all the costumes are perfectly clean and look brand new. It never feels like the West to me; it all just feels like a stage play. And yet 1940s film noirs don't feel like that at all in my opinion. My point is that I have no nostalgia for these Westerns and my opinion on them is entirely ignorant and most likely wrong. So this isn't exactly a recommendation; it's more of a rant.
The main plot of this movie is about a greedy land-owner trying to take over a neighboring ranch. There's a minor sub-plot about a couple people dying with bite marks on their neck, but that's never really investigated or even discussed. Anyway, while this small-time ranch is trying to hold out from being bullied into selling their land, a mysterious gunslinger shows up to help. As backstory, he happens to be a vampire. But he isn't exactly the villain of this movie and he isn't exactly terrorizing anyone. He literally spends all his time trying to help the small ranch fight back against the greedy land-owner. But the local preacher (who's in love with the ranch owner's daughter) doesn't like the gunslinger and wants him gone. Honestly, you could cut out all the parts about the gunslinger being a vampire and very little of this movie would change. The gunslinger could've just been a "sinner" and 90% of this movie would still be the same.
Anyway, if you're curious at all about watching the very first vampire western, here's a trailer. You can watch the movie right now on tubi.
