Thus, rough-shod the trapper broke the wilderness, fathomed its secret places, traversed its trails and passes, marking them with his own blood and more vividly with that of the natives.

Incidentally, by right of their discoveries and occupation of the wilderness, much of it became by the law of nations a part of the lands of the United States, though still nominally claimed by Mexico.

Two years after the return of the famous Lewis-and-Clark expedition, Andrew Henry "discovered" South Pass (1808), and led his party through it into the Green River* Valley.

His discovery consisted, like many others of the time, in following up the bison trails and the highways of the natives.

The latter, of course, knew every foot of the whole country; each tribe its own special lands and more or less into and across those of its neighbours.
* The name Green River was used as early as 1824, and was probably derived from the name of the early trapper.