Hi,

Having learned this one before being taught English, I hear it as:
"I'm leaving ol' Den".
I didn't know the two daughters version, but if Bill Jones lived close enough to Denver that one of his daughters would go there leaving home, that would sort of fit, I guess, except:
I don't know about cowboy history; would it make sense for a cowboy, or maybe a former farmer, to travel from Denver to Montana to go work with horses?

Other than that:
* I don't think he's travelling to Montana to party. If his target was for partying, I would expect it to be a specific city or town.
* I agree the "they" are horses, not dogies. Cows, after all, have tails that are mostly skin; their tails wouldn't get all matted. Horses, however, have tails that are mostly made of hair. Their tails would indeed get matted on a long and hard journey, unless taken good care of.
If their backs also get raw, does that mean "they" are the horses that carried the riders and packs? Or would that fit for wagon horses as well (assuming those two verses started their live together)?

And then: When did pool rooms start? (Pool rooms with fighting, to be precise?)

Bye,
                                                                Mysha