Morro Rock, a State Historic Landmark, was formed about 23 million years ago from the plugs of long-extinct volcanoes. Morro Rock was an important navigational aid for mariners for over 300 because the rock is approximately 576 feet tall which made it the most visible in a chain of nine peaks. Portuguese explorer, Juan Rodriguez Cabrillo named the rock “El Morro” in 1542. In Spanish "Morro" means crown shaped hill. Morro Rock, sometimes called the “Gibraltar of the Pacific,” is the last peak of the Nine Sisters, which extend from San Luis Obispo to Morro Bay. 

The rock itself was mined on and off until 1963. Morro Rock provided material for the break water of Morro Bay and Port San Luis Harbor. In 1966 a bill was introduced which transferred the full title to the State of California. Later the San Luis Obispo County Historical Society and the City of Morro Bay succeeded in getting the Morro Rock declared as California Registered Historical Landmark #821. Morro Rock also became State Landmark #801 in 1968. The rock has since been designated a bird sanctuary for the Peregrine Falcon and other bird species.