“For the better part of a mile we kept to the edge of the bluffs, separating and spreading over a wide strip of territory as we hunted for the place where our maps showed that a right-hand fork of the trail made its descent to the river bottom. . . .
The men were the first to find the descent, which is merely a steeply washed break in the bluffs. But it bore evidence that the wagons had descended at this point and it is called (we found later) Mexican Hill.
[N.B. The mileage is an approximation. Mexican Hill appears to lie somewhere between the Pony Express Bikepacking Route and the North Platte River off one of the tangential dirt roads. More info here . . .]