It was a grant of 48,612 acres (19,673 ha) by Governor Juan B. Alvarado to Antonio del Valle, a Mexican army officer, in recognition for his service to Alta California.

The adobe headquarters of the rancho, and the site of the gold find (known today as the "Oak of the Golden Dream"), are designated California Historical Landmarks.

According to a local legend, Francisco López, the uncle of Antonio's second wife, Jacoba Feliz, took a rest under an oak tree in Placerita Canyon on March 9, 1842, and had a dream that he was floating on a pool of gold.

[6] Contrary to this portrait of him as a farmer who stumbled upon his discovery, López had studied mineralogy at the University of Mexico and had been actively searching for gold.

[9] After their release, Bidwell headed north through Placerita Canyon, saw the mining operations, and was determined to search for gold on his way to Sutter's Fort.

[1] With the cession of California to the United States following the Mexican-American War, the 1848 Treaty of Guadalupe Hidalgo provided that the land grants would be honored.

[15][16] Unfortunately, at this time Southern California experienced a great deal of flooding, and ranchers were forced to mortgage their properties in order to sustain their needs during the interruption in producing their food and needs and other damages to the land and buildings.

[15] Finally, in 1862 Del Valle was forced to sell off most of his land to oil speculators (the Philadelphia and California Petroleum Company headed by Thomas A. Scott), keeping only his Rancho Camulos.

[17] The oilmen were unable to find any oil, and Rancho San Francisco eventually landed in the hands of Henry Newhall, whose name is now closely associated with the Santa Clarita Valley area.

Here, in January 1850, William Lewis Manly and John Rogers obtained supplies and animals to rescue their comrades in a California-bound gold-seeking emigrant party that was stranded and starving in Death Valley, some 250 miles to the northeast.

While gathering wild onions near an oak tree in Placerita Canyon he found gold particles clinging to the roots of the bulbs.