[3] The name of the unincorporated community Shelter Valley is typically used both locally and by the media to refer generally to the geological feature of Earthquake Valley, and it is common for both names to be referenced in publications after the 1962[2] establishment of the subdivision.
Earthquake Valley, then called the Valle de San Felipe, became the route of the Sonora Road into the coastal region of Southern California.
From the time of the Mexican American War and the California Gold Rush the Sonora Road became the route of the Southern Emigrant Trail that passed through the valley from Blair Valley to Teofulio Summit, (formerly Warner Pass).
This trail remained the major southern route into California from the eastern United States until the advent of the railroad at Yuma, Arizona in 1877 reduced its importance.
From 1858 the important San Felipe Station of the Butterfield Overland Mail was located about a quarter mile north of Scissors Crossing.