The
Santa Rosa Plateau became Rancho Santa Rosa under an 1846 Mexican land grant to cattle and sheep rancher Juan Moreno. 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, and the grant was patented to Juan Moreno in 1872. 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. A large portion of Rancho Santa Rosa lands were purchased to create the
Santa Rosa Plateau Ecological Reserve. It was assembled in several stages by
The Nature Conservancy in 1984. Subsequently parcels were purchased in the 1990s by the
State of California, the Riverside County Regional Park and Open Space District, and the
Metropolitan Water District of Southern California. ==Historic sites of the Rancho==