The Sweetwater has its headwaters in the southern end of the Wind River Mountains. For several miles at South Pass it flows southeast just barely on the Atlantic side of the continental divide (coming within a mile of the divide itself). Then, at this spot, the Sweetwater makes its decisive turn to the east.

It is also at this spot, within sight of (and essentially the same elevation as) the dividing point between Atlantic and Pacific drainages, that the trail leaves the Sweetwater behind.