"Where you from? (adult)" joke

A young fellow at the state fair stood watching an old indian. Above the old indian was a sign that read, "$5.00 - If I can't tell you where you're from, I'll pay you $50.00!".
The young man watched a cowboy approach the indian and ask, "Is the sign right?".
The indian says, "yes".
The cowboy hands him a five and says, "you're on!"
The indian looks the cowboy up and down, noticing some cow dung on his boots and flatly states, "you're from Wyoming!".
The cowboy shakes his head and says, "I'll be darned! You're right!" and strolls away.
A second cowboy approaches the indian and goes through the same routine. Handing him the fiver, he stands and watches as the indian looks him up and down and notices a bit of straw and cow dung on his boots. The indian says, "you're from Montana!"
The cowboy, dejected as all get out, walks away.
The young man decides he's going to give the indian a run for the money. He goes into the mens room, takes his boots off, scrubs them up, dries them off, puts on a coat of polish and approaches the indian. He hands the indian a five dollar bill and says, "do your stuff!"
The indian looks and looks, up and down, and appears to be befuddled.
The young man is now thinking he's gone one up on the indian.
The indian says, "You're from Texas!"
The young man gets really upsent and can't for the life of him figure out how the indian could know that, so he asks, "How in the world did you know I'm from Texas?"
The indian replies, "by the wool on your zipper!"