I'm finding a lot of small adventures but nothing in the way of an extended campaign for an old west game, supernatural or otherwise. Anybody seen one? Drop a link?
Burned Bush Wells for Boot Hill comes to mind right off. Nice little campaign area to work with.
Down Darker Trails uses Call of Cthulhu 7E as a core system
The Call Of Cthulhu Keepers Book is necessary for the core mechanics: https://www.chaosium.com/call-of-cthulhu-keeper-rulebook-7th-ed-hardcover/
Although at a stretch perhaps just the Call of Cthulhu 7E Quickstart may have enough framework for the rules: https://www.chaosium.com/call-of-cthulhu-7th-edition-quick-start-rules/
Down Darker Trails is essientially an era-setting book for Call of Cthulhu, but it can be easily played without the supernatural edge as well.
This is quite a good YouTube review: https://www.youtube.com/watch?v=RO6tN0Jk6xc&t=573s
Looks like a adventure resource for it has now been published, it's a collection of separate adventures in one detailed geographical region, but it's not an actual campaign: Shadows Over Stillwater: https://www.chaosium.com/shadows-over-stillwater-pdf/
What abput Werewolf: Wild West? I have the book from another player. but have not yet had a chance to look at it.
Deadlands: https://www.peginc.com/product-category/deadlands-reloaded/?orderby=popularity
For Savage Worlds has a decent number of plot point campaigns. Idk of any pure Westerns though.
Not that I know of. Anyways, I've just made my own fully historical campaign by researching the real history of the West and just playing there.