Rancho Jamacha was a 8,881-acre (35.94 km2) Mexican land grant in present-day San Diego County, California, given in 1840 by Governor Juan Alvarado to Apolinaria Lorenzana.
[3][4] 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.
[7] Unlike northern California, where gold seekers constituted the majority of new emigrants, military men made up most of the Americans in the San Diego area following the Mexican–American War.
Among the newly arrived military personnel were Colonel John Bankhead Magruder, First Lieutenant Asher R. Eddy, Eugene B. Pendleton, Frank Ames, and Robert Kelly.
Robert Kelly (1825–1890) was a native of the Isle of Man who came to the United States with his family in 1841, and arrived in San Diego in 1851.
In 1853, Colonel Magruder purchased the Rancho Jamacha from Lorenzana, and sold an undivided two-thirds to Eddy, Kelly, Ames, and Pendleton.