Clearly, I needed more information. I read everything on Forrest Fenn’s website, oldsantafetradingco.com. Then, I ordered THE book, The Thrill of the Chase.
Photo taken in the Yellowstone area. (Photo credit: Wikipedia)
Before it arrived, I thought, wouldn’t it be brilliant if he hid it somewhere along the Continental Divide; that’s where all waters halt. Or maybe at a junction of boundaries, like the Four Corners in the Southwest, or the three corners of more northern states. Maybe that’s why the GPS, so you’d know when you arrived. So my next (armchair) plan landed me in the northwest quadrant of Yellowstone Park, a bit of a hike in grizzly country, but after all, there was bound to be marvelous gazing to be had. Furthermore, that hear me all and listen well put me in mind of an echo, and I found one of those on the map, too.
And then, the book arrived….
The Fenn Diagrams 
Continental Divide that’s where all waters halt
Could you pls explain, why all waters halt here?
In relation to the next step (“take it in the canyon down”), my thinking at the time
was water runs downhill, so, for instance, the warm waters of the Gulf of Mexico could never have been any farther west than the Continental Divide in the mountains north of Santa Fe. And that’s definitely water high in my mind, but probably not what Forrest had in mind, eh?