The Nine Sisters or the Morros are a chain of nine volcanic peaks and hills between Morro Bay and San Luis Obispo, California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

. They are popular with photographers and rock climbers. Their volcanic origin makes them of significant geological interest. They support a wide variety of plant, animal, and bird life. Two of the peaks are in Morro Bay State Park

Morro Bay State Park

Morro Bay State Park is a state park in Morro Bay, in western San Luis Obispo County, California. On the bay’s northeastern edge, there is a saltwater marsh that supports a thriving bird population. -Recreation:...

.

The peaks were created over 20,000,000 years ago as volcanic plug

Volcanic plug

A volcanic plug, also called a volcanic neck or lava neck, is a volcanic landform created when magma hardens within a vent on an active volcano. When forming, a plug can cause an extreme build-up of pressure if volatile-charged magma is trapped beneath it, and this can sometimes lead to an...

s of magma

Magma

Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

 which welled up and solidified inside softer rock which has since been eroded. The highest peak is Bishop Peak at 1,559 ft.

Peaks

The peaks in order from Morro Bay to San Luis Obispo including their height.

1. Morro Rock
   Morro Rock
   Morro Rock is a volcanic plug located just offshore from Morro Bay, California, at the entrance to Morro Bay Harbor. A causeway connects it with the shore, effectively making it a tied island. The area surrounding the base of Morro Rock can be visited. The rock is protected as the Morro Rock State...
   
    576 ft
2. Black Hill 665 ft
3. Cabrillo Peak
   Cabrillo Peak
   Cerro Cabrillo, also known locally as Cabrillo Peak, is a rocky butte in Morro Bay State Park, California. The rock outcrop, composed mostly of rhyodacite, is a volcanic plug formed when magma welled up underneath a layer of softer rock and solidified...
   
    911 ft
4. Hollister Peak
   Hollister Peak
   Hollister Peak is a volcanic plug located near Morro Bay, California. It is one of the Nine Sisters, and receives its name from the family that lived at its base in 1884. It was of religious importance to the Chumash. As of 2011, there is no public access to Hollister Peak....
   
    1,404 ft
5. Cerro Romauldo
   Cerro Romauldo
   Cerro Romauldo is a hill in San Luis Obispo, California. The hill is the fifth in a series of volcanic plugs called the Nine Sisters. Until 1964 the hill was officially known as Romualdo Peak....
   
    1,306 ft
6. Chumash Peak
   Chumash Peak
   Chumash Peak is a hill in San Luis Obispo, California. The peak is the sixth in a series of volcanic plugs known as the Nine Sisters. In 1964 the hill was named in recognition of the Chumash Indians who lived in the area due to efforts by Louisiana Dart, curator of the San Luis Obispo County...
   
    1,257 ft
7. Bishop Peak 1,559 ft
8. Cerro San Luis
   Cerro San Luis
   Cerro San Luis Obispo is a mountain in San Luis Obispo, California. It is part of the chain of peaks called the Nine Sisters, and is often referred to as San Luis Mountain, Mount San Luis, or Madonna Mountain. It is a popular spot for mountain biking and hiking, offering spectacular views and...
   
    1,292 ft
9. Islay Hill
   Islay Hill
   Islay Hill is a volcanic cone and is the southernmost of the nine major morros that make up the Nine Sisters. This chain of extinct volcanoes stretches from Morro Bay in San Luis Obispo County, California....
   
   775 ft