Rancho Agua Caliente was a 3,219-acre (13.03 km2) Mexican land grant in present day Sonoma County, California given in 1840 by Governor Juan Alvarado to Lázaro Piña (often misspelled as "Pena" in historical documents).
By 1840, Vallejo's staff consisted of Colonel Victor Prudon, Major José de los Santos Berreyesa, and Alfarez (second lieutenant) Lázaro Piña.
Lázaro left California soon after the beginning of the Mexican-American War and was killed fighting on the Mexican side at the Battle of Cerro Gordo in 1847.
[6] 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.
[11] After the Mexican-American War Joseph Hooker retired from the United States Army and bought a part of the rancho in 1853.