This is pretty fun. Scientific American has dug out of its files a 1901 story (with photographs) about interesting rock features on the Southern California coast. Included are the arch that used to be on the beach north of Santa Monica and the former "Sentinel Rock" on Pt. Fermin in San Pedro. The magazine called it "Firman" in those days.
Here's a beach-eye view from the other angle, dated about 1880, from the USC Digital Library, and an image from the Santa Monica Public Library.