The Santa Rosa Plateau became Rancho Santa Rosa under an 1846 Mexican land grant to cattle and sheep rancher Juan Moreno.[5]
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. As required by the Land Act of 1851, a claim for Rancho Santa Rosa was filed with the Public Land Commission in 1852,[6][7] and the grant was patented to Juan Moreno in 1872.[8]
Moreno sold the rancho to Augustin Machado in 1855. Machado subsequently purchased neighboring Rancho La Laguna in 1858. In 1876, Rancho Santa Rosa was sold to Englishman John Dear, who had sent his son, Parker, from England to inspect the rancho lands. He stayed to run it for the next 18 years, trying to make it a profitable venture. Flood events that twice destroyed the railroad connection of the California Southern Railroad with San Diego, cutting economical transportation to and from his ranch and development projects at Linda Rosa. Parker Dear was forced to put the ranch into receivership in 1894. Walter Vail, already a successful ranch owner in Arizona and owner of Santa Rosa Island, bought Rancho Santa Rosa in 1904. The Vails continued to operate their cattle ranch for the next sixty years. In 1964, the Vails sold the ranch to the Kaiser Steel Company, which master-planned Rancho California - the communities that today comprise the cities of Temecula and Murrieta.
Moreno and Machado Adobes. Two unrestored mid-19th-century rancho adobes that are Riverside County’s oldest standing structures. Also nearby are the Vail Ranch Barn, the ranch foreman's house, the ruins of the Dear - Vail Ranch-house and a Luiseno village site.[9]
^Ogden Hoffman, 1862, Reports of Land Cases Determined in the United States District Court for the Northern District of California, Numa Hubert, San Francisco
Lech, Steve (2011). More Than a Place To Pitch a Rent: The Stories Behind Riverside County's Regional Parks. Riverside, CA: Steve Lech. p. 150. ISBN978-0-9837500-0-0. OCLC768249467.