The Bancroft Ranch House was constructed by Augustus S Ensworth, Justice of the Peace, in approximately 1856, out of timbers salvaged from a ship wreck in San Diego Bay. When he died, the adobe ranch house was purchased by Rufus King Porter, son of the founder of Scientific American, who gave Spring Valley its name. H H Bancroft purchased the property, now known as The Bancroft Ranch House, from Porter in 1885 and owned it until his death in 1918.
Hubert Bancroft also bought additional properties in the locality and in doing so amalgamated over 500 acres of farm land. He subsequently built a more comfortable family home up the hill from the ranch house and also a rock school house for his children which is now located across the street.
It is uncertain as to whether or not Bancroft wrote any of his books whilst staying at the Spring Valley ranch. While some historians believe that he did write some of his works here, others believe that the ranch was merely a holiday home where Hubert Bancroft came on vacation.
The Bancroft House is now a state and national historic landmark.