After a decline in use for filming by the 1950s, its owner George Spahn established a stable for renting horses for riding on the varied acres.

After Spahn's death and a wildfire that destroyed the main ranch house and outbuildings, the land was incorporated into the Santa Susana Pass State Historic Park.

[1] Beginning in the 1880s, a piece of land, including what would later become the Spahn Ranch, became the homestead of Mexican immigrant Dionisio Sánchez and Hoosier James R. Williams, along with their families.

Among the productions said to have been filmed at Spahn Ranch are The Lone Ranger with Clayton Moore,[6] and several episodes of the Bonanza television series.

[10] Spahn was 80 years old, going blind and living at his ranch when he allowed the Manson Family to move in, rent-free, in exchange for labor.

"[13] In the 1970 murder trial, Prosecutor Vincent Bugliosi later claimed that Manson would occasionally send one of his girls to Spahn for sexual relations.

[15] On August 16, 1969, after the Tate–LaBianca murders, more than one hundred officers from the Special Enforcement Detail (the SWAT team of the Los Angeles County Sheriff's Department) were deployed at Spahn Ranch in what authors Tom O'Neill and Dan Piepenbring [de] have alleged was the largest documented police raid in California history in their book CHAOS: Charles Manson, the CIA, and the Secret History of the Sixties, resulting in the arrest of several Manson Family members due to suspicion of their participation in an automobile theft ring (unrelated to the later arrest of those involved in the murders).

[16][17] Ten days later, on August 26, Susan Atkins of the Family lured Shea to a remote spot on the ranch where he was ambushed and killed by Bruce M. Davis and Steve "Clem" Grogan.