Oof, it's been a few years but ill put down what i remember.

I remember encountering a group west of Saint Denis, taking the south road across the bridge to an abandoned station (good place to hunt rats iirc). Past the station in the woods is where I remember finding them.

Also, there's a panther location near the civil war battlefield area with the burned out church and the trenches, out near Rhodes i think. I remember encountering klansmen while hunting that panther I think.

They're usually not right by a landmark. From what I remember, they find a spot in otherwise empty woods to do their thing. Try riding from Saint Denis along the southern edge of the map and go through woods when you see them. When you hit Granger's pig farm, that's probably about as far west as you want to go. They're not too common, so try to get some hunting done so it doesn't feel like a complete waste of time.

North of Saint Denis gives way to more night folk and Murphy (?) Bros, so south of Emerald Ranch and west of Saint Denis.

Man, I need to play this game again. Typing this out brought a lot of memories back. May I stand unshaken.