[1] Rancho El Tejón, a large 1843 Mexican land grant in the Tehachapi Mountains, was headquartered below the pass along Tejon Creek.

Eventually, a road running straight north (from Elizabeth Lake), across westernmost Antelope Valley, and then over this Tejon Pass evolved.

This route to the pass diverted from the El Camino Viejo at Elisabeth Lake, and from 1849 to before 1854 it was the main road connecting the southern part of the state to the trail along the eastern side of the San Joaquin Valley to the goldfields to the north.

[2] In 1853, the road which used the Old Tejon Pass was surveyed by Robert Stockton Williamson of the U.S. Army for suitability as a rail-bed for the planned transcontinental railroad into California.

Williamson scouted it and found it would be far more suitable for rail lines and wagons if the bulk of the traffic henceforth went that way.