Rancho Las Posas was a Mexican land grant in what is now Camarillo, Moorpark, portions of Simi Valley, and portions of the Oxnard Plain in Ventura County, California. It was awarded by Governor José Figueroa to José Antonio Carrillo in 1834. Rancho Simi (also known as Rancho San José de Nuestra Señora de Altagracia y Simí) was another Spanish land grant that covered much of Simi Valley and land in what is now western Los Angeles County. The land grant was held by the Pico family. Much of this land would eventually be purchased by the de la Guerra y Noriega family of Santa Barbara.

Rancho Simi, as well as several other properties in the region, were purchased by Pennsylvania-based land speculator, railroad executive, and businessman Thomas A. Scott. Thomas R. Bard moved west to manage Scott’s holdings in California and would later come to own much land in Ventura County. In the 1880s Bard would form the Simi Land and Water Company to sell and lease portions of the large ranch. The Santa Clara Water and Irrigating Company was not strictly a Bard-owned enterprise. However, he was greatly involved in much of the development of the area covered in this collection. The Las Posas and Simi Valley area continued to be dominated by agriculture and ranching, including sheep, cattle, wheat, and barley. In the years leading up to the 1960s Simi Valley began to diversify its agriculture to include citrus, walnuts, and apricots until the advent of suburban development in the 1960s.