The Nine Sisters and Morro Rock – Volcanic plugs – Morro Bay to San Luis Obispo

4 of the 9 sisters - volcanic plugs

The Nine Sisters:  Lesser known siblings of Morro Rock

The Nine Sisters – a chain of volcanic plugs stretching from Morro Rock to San Luis Obispo.

A beautiful sunset over the Los Osos ValleA Great sunset view of a few of the “Sisters”

This week’s Photo of the Week was taken of the chain of peaks that runs from the City of San Luis Obispo and ends at Morro Rock.

This chain, called the “Nine Sisters” or sometimes the “Seven Sisters”, is a group of volcanic plugs. This is what’s left of an extinct volcano when its ash and lava are eroded away. This is the magma that was left in the throat of the volcano when its fires went out.This chain starts with the oldest, Islay Peak, back by the San Luis Obispo airport. Not all of the peaks are named on maps, nor are there just nine of them, but “nine” or “seven” sisters sounds better than “twenty-three sisters”.

These peaks really define the area in a special way. Morro Bay would be a nice harbor town without the rock, but not as special as it is.

Hiking some of the Nine Sisters

Bishops Peak towers over San Luis Obispo and Cal Poly and is a guidepost wherever you might be in town. This peak is open for hiking and many take advantage of the lovely views available from the top. Here is a link to EveryTrail with more information.

If you drive from San Luis Obispo to Los Osos on Los Osos Valley Road, you will pass some of the prettiest agricultural fields anywhere. The soil is as black as any I’ve seen anywhere and produces beautiful crops.

Los Osos Valley farmers produce vegetables, but the real spectacular crop are the flower seeds produced at the western end of the valley. They have harvesters which are basically giant vacuum cleaners, going along numerous rows and sucking up the seeds that will make their way to the little packages that you find in stores.

The sisters can also be viewed from Highway 1 as it moves away from Highway 101 in San Luis Obispo toward Morro Bay. This route is to the north of and parallels Los Osos Valley Road.

View of Morro Bay Rock and beach


Hiking is strictly prohibited on Morro Rock, but its closest sister, Black Hill, is part of Morro State Park and has hiking trails. The picture at the top of the Beach Cities page was taken from Black Hill.

Highway 1, Highway 101, Los Osos Valley Road – any route by which you come to this area will give you great views of this beautiful and interesting chain of peaks.



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