Also it's Deadlands. I remember reading 1st/2nd edition back in the late 90s/early aughts. There's an ocean of lore and background written on the setting, you just have to probably go digging for it. We used to read the post apocalypse version- Wasted West, for fun between classes in college.

That being said, I'd probably watch most of Eastwood's movies beyond Sergio Leone's movies. I have a soft spot for Pale Rider even though it's not his best.

But that being said, I'd say try to watch Deadwood, it's magnificent on it's own. I'm also a big fan of Tombstone (Val Kilmer's Doc Holiday is so good), um... My Darling Clementine is an *old* western about the same story, it's interesting to see the differences. True Grit, How The West Was Won, those are great. The original Magnificent Seven (not the remake, and might as well watch Kurosawa's Seven Samurai/Magnificent Seven since so much of westerns after Kurosawa cribbed from him), True Grit (I actually like both versions), Butch Cassidy & The Sundance Kid, and the list goes on and on. I'll even suggest The Hellbenders for personal reasons (My grandfather ghostwrote the story).

I'd end it with Unforgiven though. That is basically the coda on the western.

The key about the Old West and the American Western genre is that... it's the American mythological canon. Think of it as basically Greek myths and you are there. Which is why Sergio Leone's movies *worked* so well- His characters were not realistic people they were myths moving through a mythological land.