Opening the Iron Trail by Edwin L. Sabin

IT was the easy Rattlesnake Pass that finally led out from the farther edge of the great Laramie Plains, and down to the North Platte River.

"There's the last of the main streams which flow eastward, men," remarked General Dodge, as from the top of the pass they emerged into view of the valley below. "Once across that, and over the next plateau, and we'll be into the unknown country."