You really don't need much except a map, creatures, a rule system, and a goal.
And since this little idea has infected my brain I might be able to add more like an ornery head rat named "Old William", a Unseelie rattle rustler named "Great Auntie Oakleaf" replete with spurs and a giant silver belt buckle that says "Ride 'em Hard, Leave 'em Wanting", PC complications like a failed relationship, older sibling got the farm, orphan, and trouble with the law.
Here is a nice document on Oklahoma cattle drives which seems very gameable: https://www.okhistory.org/historycenter/forms/tdcattledrives.pdf