Rancho San Francisco was a land grant of 48,612 acres (197 km2) by Governor Juan B. Alvarado to Antonio del Valle, a Spanish army officer, in recognition for his service to the state of Alta California. The rancho was the location of the first documented discovery of gold in California in 1842. The current cities of Santa Clarita, Valencia, and Piru lie within the boundaries of Rancho San Francisco, later known as Newhall Ranch. The rancho is a designated California Historical Landmark.
After Mission San Fernando Rey de España was established in 1797, the administrators there realized they would need more land for agriculture and livestock, and they looked north to the Santa Clarita Valley to establish their estancia, or mission rancho. Subsequently, the Tataviam Indians who had been living there were relocated to the Mission, where they were baptized and put to work. The Estancia de San Francisco Xavier was built in 1804 at the confluence of Castaic Creek and the Santa Clara River.