With the outbreak of the American Civil War in April 1861, there were concerns on the Union side about the loyalty and security of the Los Angeles area.

A traditional thoroughfare of desert-dwelling Native Americans, the Mohave Trail much later served Spanish missionaries, explorers, and foreign colonizers and settlers from the 18th to 19th centuries who called it the Mojave Trail, and ran between watering holes across the Mojave Desert between the Colorado River and Mojave River then following it to the Cajon Pass, the gap between the San Bernardino Mountains and San Gabriel Mountains, into Southern California ending at Drum Barracks.

[3] Francisco Garcés, the Spanish Franciscan missionary, traveled the trail with Mohave guides, after leaving the expedition of Juan Bautista de Anza in 1776.

José María de Zalvidea, the zealous Franciscan administrator of Mission San Gabriel also crossed the trail in 1806, reportedly converting five indigenous Mohaves near present-day Hesperia.

The old road from Fork of the Road eastward along the Mojave River is interrupted after 10.9 acres (4.4 ha) by private property, below the site of the old Camp Cady (on the north bank of the Mojave River, roughly 12 miles (19 km) northeast of Newberry Springs, California).

Under optimal conditions, its full length of 133 miles (214 km) from Beale's Crossing to Manix Wash can be travelled in 2 to 3 days.

The army protected the settlers and travelers from the attacks of the resident Paiute, Mojave, and Chemehuevi Native Americans until 1871.

[7] Upon reaching the San Bernardino Valley of California, Smith and Abraham LaPlant (who spoke some Spanish) borrowed horses from a rancher and rode to the San Gabriel Mission on November 27, 1826, to present themselves to its director, Father José Bernardo Sánchez, who received them warmly.