Historically associated with a network of royal roads (caminos reales) used by inhabitants of New Spain, the modern commemorative route in the U.S. state of California is named after these roads, with its southern terminus at Mission San Diego de Alcalá and its northern terminus at Mission San Francisco Solano in Sonoma, California.

These various caminos reales covered much of what is today California, but with no single special route designated to link the missions.

Proceeding north, Portolá followed the coastline (today's California State Route 1), except where forced inland by coastal cliffs.

On the return trip to San Diego, Gaspar de Portolá found a shorter detour around one stretch of coastal cliffs via Conejo Valley.

[citation needed] Portolá journeyed again from San Diego to Monterey in 1770, where Junipero Serra (who traveled by ship) founded the second mission (later moved a short distance south to Carmel).

The Juan Bautista de Anza expedition of (1775–76) entered Alta California from the southeast (crossing the Colorado River near today's Yuma, Arizona), and picked up Portolá's trail at Mission San Gabriel.

[4] While it is sometimes claimed[citation needed] that mission settlements were deliberately spaced approximately 30 miles (48 kilometers) apart to facilitate overland travel via horseback during the Spanish era, this claim is not made in any historical sources and first appeared in 20th-century advertising materials encouraging automobile travel along the route.

For example, ash trees were the marker for where a spring was to be found, as seen to this day at the church of Nuestra Señora del Tránsito [Wikidata] in Fresnillo, Zacatecas.

[citation needed] By the mid-nineteenth century, when California became a state, the route had been improved in certain sections, but was wholly inadequate for large stagecoaches and freight wagons.

[8] In the early twentieth century, organizations and government agencies became interested in creating official designations or commemorations of roads and highways.

Given the lack of standardized highway signs at the time, it was decided to place distinctive bells along the route, hung on supports in the form of an 11-foot (3.4 m) high shepherd's crook, also described as "a Franciscan walking stick".

[11] A 1915 map produced by the Automobile Club of Southern California traced the route that connected the missions for motorists to follow.

[15] Permits issued by Caltrans for installations along state routes have detailed specifications on how the bell should be set up for safety and legal considerations.

[23] The issue was also present when the statues of Junípero Serra were damaged and/or removed in 2020 during the George Floyd protests which expanded to include monuments of individuals associated with the controversy over the genocide of indigenous peoples in the Americas.