I grew up in Montana, not far from one of the routes Lewis and Clarke took through that state. The legend of John Colter is still alive there. Every year, Montanans hold the John Colter run to commemorate his escape.

http://winddrinkers.org/trailhead/races/john-colter/

I’ve done that race, it’s awesome. Wading across the river when your legs are shot from the run is especially exciting...

Ah, but do they run like Colter did? Naked and bleeding, chased by the Blackfeet tribe.

Never heard of him or or story. But reading about his escape I immediately thought of the run in apocalypto.

Flynn treasure. The poem basically says it's at some damn or waterfall. Would be cool if the spot was chosen from the tale of the 'original great American adventurers'