Rancho Suey was a 48,834-acre (197.62 km2) Mexican land grant in present day southern San Luis Obispo County and northern Santa Barbara County, California given in 1837 by Governor Juan B. Alvarado to María Ramona Carrillo de Pacheco. The grant was east of present day Santa Maria and extended along the San Luis Obispo-Santa Barbara County line, and between the Santa Maria River and the Cuyama River.
Captain José Antonio Romualdo Pacheco (–1831), came from Mexico to California in 1825, and served as an aide to Governor José María de Echeandía. In 1826, Pacheco married María Ramona Carrillo de Pacheco (1812–1888), a daughter of Maria Ygnacia Lopez de Carrillo, the grantee of Rancho Cabeza de Santa Rosa. María Ramona Carrillo was a sister-in-law of General Mariano Guadalupe Vallejo. Pacheco died defending the widely despised centralist Mexican governor of California, Manuel Victoria, at the Battle of Cahuenga Pass in 1831.
His widow, María Ramona Carrillo de Pacheco was given the five square league Rancho Suey land grant by Governor Alvarado in 1837. In 1837, she married Captain John Wilson (1797–1861), a Scottish-born sea captain and trader, who came to California in 1830. John (Juan) Wilson raised Pacheco's son Jose Antonio Romualdo Jr. Wilson was the grantee of Rancho Los Guilicos in Sonoma County. Wilson and his business partner, James Scott (-1851), also owned Rancho El Chorro and Rancho Cañada de los Osos y Pecho y Islay. In 1845, Wilson built an adobe home on Rancho Cañada de los Osos y Pecho y Islay and lived there with his family until his death in 1860.
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 Suey was filed with the Public Land Commission in 1852, and the grant was patented to María Ramona Carrillo de Wilson in 1865.
- Ogden Hoffman, 1862, Reports of Land Cases Determined in the United States District Court for the Northern District of California, Numa Hubert, San Francisco
- Diseño del Rancho Suey
- Santa Barbara County Rancho Map
- Maria Ygnacia Lopez de Carrillo
- Ramona Carrillo de Pacheco de Wilson
- Martha Voght,Scots in Hispanic California, The Scottish Historical Review, Vol. 52, No. 154, Part 2 (Oct., 1973), pp. 137-148, Edinburgh University Press
- Hoover, Mildred B.; Hero & Ethel Rensch, and William N. Abeloe (1966). Historic Spots in California. Stanford University Press. ISBN 978-0-8047-4482-9.
- United States. District Court (California : Southern District) Land Case 14 SD
- Report of the Surveyor General 1844 - 1886
- Newhall, Ruth Waldo (1992). A California Legend: The Newhall Land and Farming Company. Newhall Land and Farming Company.