Sierra Club San Luis Obispo

One Earth, One Chance
Morro Rock, Home of the Peregrine Falcon

The Nine Sisters 
San Luis Obispo 

Bishop Peak Trail Work

[Volcanic Chain]
View of Nine Sisters Volcanic Chain



The Morros figure prominently in the life of county residents. From many homes, the tawny slopes of Bishop Peak or other Morros can be seen.

These mountains are at the very heart of San Luis Obispo county. They give us shelter from the perennial wind, constant visual contact with nature, "a sense of place" and a daily reminder that we still live close to the land.

A group of Sierra Club members hiked to the top of Cerro San Luis Obispo (San Luis Mountain). They watched the lingering sunset followed by the rise of a full moon, and the views out over the valleys that intersect below, and this showed the reasons why all of us should be concerned for the future of the Morros. A pall of yellow haze was trapped by a typical spring inversion layer over Price Canyon to the south, probably generated by diesel and gas emissions from oil wells. Pacific Gas and Electric Company power lines snaked their way over the Los Osos Valley. And as the lights came on in neighborhoods below, they illuminated the assault of the growing city against its embracing peaks and hillsides.

What will it truly mean to try to "save the peaks?" In the case of the Nine Sisters, we must look for a unique solution for the peaks are too important a resource to risk a bruising (and ultimately, losing) battle.

Our ultimate goal is to preserve the character, historic value, and the flora and fauna of this beautiful chain of peaks. With the cooperation of the property owners, the State of California, and local city and county government agencies, and the public at large, the Morros can be preserved for future generations.

On the whole, the Morros can continue to be a fundamental part of a "picture postcard" landscape of San Luis Obispo County. The existing landowners— many of them third- and fourth- generation descendants of the original land grantees — are good stewards of the peaks. We should take whatever time is necessary to work with them to resolve the future of the peaks. But we should not hesitate to start down the road.

Overview of the Nine Sisters

The Nine Sisters of San Luis Obispo County, also known as the Morros, are a unique set of landmarks between the city of Morro Bay and the City of San Luis Obispo. These ancient volcanic mountains are very scenic and deserve preservation now and into the future.

The Nine Sisters are a series of ancient volcanic peaks which form a backdrop for the Cities of San Luis Obispo and Morro Bay on the Central Coast of California. Forming a divider between the Los Osos Valley and Chorro Valley, these peaks extend from Islay Hill within the City of San Luis Obispo to Morro Rock, often called the sentinel of the Pacific Ocean, covering approximately 40 square miles. The peaks are aptly named the Nine Sisters because they are all in a row, and in close proximity. The nine have had their names designated on the Geological Survey maps since 1964. Stunted Terrace Hill and submerged Davidson's Seamount are omitted. A vicinity map of "The Nine Sisters" is shown below and are also listed in table just below the map. The Nine Sisters are often referred to as the Morros.

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[Volcanic Chain]
Overview Map of Nine Sisters Volcanic Chain


The Peaks of the Nine Sisters

There are over 21 major and minor peaks in the Morros, but there are nine major peaks, hence the name The Nine Sisters. The nine major peaks are: Morro Rock, Black Hill, Cabrillo Peak, Hollister Peak, Cerro Romauldo , Chumash Peak, Bishop Peak, San Luis Mountain, and Islay Hill. The table below list the major peaks and many of the minor peaks in the Morros Chain.
Morro Peak Name Elevation in Feet Morro Peak Name Elevation in Feet
Morro Rock 576' Terrace Hill  501
Black Hill 665' Orcutt Knob  569
Cerro Cabrillo 911' Mine Hill(Righetti Hill)  563
Hollister Peak 1,404' No Name Hill(near Hollister Peak)  1,102
Cerro Romauldo 1,306' Turtle Rock(north of Cerro Cabrillo)  209
Chumash Peak 1,257' Unnamed Hill(near Chumash Peak)  810
Bishop Peak 1,559' Unnamed Hill(south of Islay Hill) 
Cerro San Luis (San Luis Mountain) 1,292'
Islay Hill 775'
Davidson Seamount -3,600' 
in the Pacific Ocean
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Significance of the Nine Sisters

The Nine Sisters represent a very rare alignment of hills, formed from the plugs of long-extinct volcanoes. They are prominent landmarks forming a unique skyline in San Luis Obispo County located between the cities of San Luis Obispo and Morro Bay.

Although the much-photographed hills are appreciated by the public for their physical beauty, they are valued by scientists and teachers as outstanding examples of the volcanic process. They have not been active for 20,000,000 years.

The impression they give to the traveler is well illustrated by this quote from Professor William Brewer of Yale University, who led a geologic reconnaissance party through the Los Osos Valley in April 1861, and climbed one of the peaks. He wrote in his diary.


"Through the plain arise many sharp peaks or rocky—buttes—rocky, conical, very steep hills, from a few feet to two thousand feet, mostly volcanic origin, directly or indirectly. These buttes are a peculiar feature, their sharp, rugged outlines standing so clear against the sky, their sides sloping from thirty to fifty degrees...A string of these buttes more than twenty in number, some almost as sharp as a steeple, extend in a line northwest to the sea, about twenty miles distant, one standing in the sea the Morro Rock rising like a pyramid from the waters."

William Brewer, 
Professor Yale University, 1861

The Morros provide a unique habitat for many animal and plant species, including the Peregrine Falcons on Morro Rock. Several plant communities exist along the chain, which, due to its orientation, has micro climates ranging from sea-spray saturated rocks, through moss draped oak forest to parched chaparral slopes. There are several rare plants along the chain of hills, which form miniature woodlands.

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Geological Features of the Nine Sisters

The chain of volcanic plugs called the Nine Sisters were formed about 20-25 million years ago. At that time there was a significant event in the history of the continent. North America, drifting westward as the Atlantic widened, had for over 100 million years been overriding the Pacific sea floor, forcing the rocks down under its western edge where they melted and merged back into the mantle. The churned geologic debris of the 'subduction' process is represented in the chaotic melanges of the Franciscan Formation that flanks the plugs. Then, at the time the plugs themselves were formed, the western continental edge collided with an ocean ridge system, causing a major change in the forces acting on the crust. Compressive forces became tensional, rocks that had been solid melted, and the magmas oozed to the surface.

Following either the lines of existing faults, or perhaps guided slabs of rock in the sheared debris of odd ocean floor material that dominated the coastal areas, the magma's rise was confined to a narrow linear zone. At the surface there would have been a line of volcanoes, all of which have vanished, stripped away by millions of years of erosion from the coastal stream that presently flank the chain of hills.

The present peaks are the plugs of congealed lava that filled the deep parts of vents for those volcanoes. Once totally encased by the older Franciscan Formation 'melanges' through which they were intruded, they are now exposed as those older but softer rocks are washed to the sea. The volcanic rock looks a little like granite in its whitish weathered state, but its true color is the gray of rocks with a lesser silica content called rhyodacite. Close observation reveals that the magma must have been almost solid as it rose through some of these events, a sort of geologic toothpaste. Weathering has cut and widened cracks into chasms on their surfaces, making the tops of some appear like a montage of boulders. Some of the peaks were doubtless much taller until comparatively recent times, from the testimony of large landslide and avalanche deposits of their flanks.

The magmatic intrusions mark the end of subduction and the birth of a new stress and faulting regime along the western edge of North America known today as the San Andreas fault system. The peaks and the Franciscan Formation in which they stand have a long story to tell us, a story that is unique in California.

There are rocks of similar age and type elsewhere in the United States, but few can be seen with ease from a paved highway. These peaks are great illustrations of the process of dike injection of magma, of the shape and form of dikes, of the movement of viscous, semi-solid magmas, of exfoliation weathering, and other volcanic features. The surrounding Franciscan melanges allow for easy inspection of the dependence of soil formation on rock type, and also illustrate very well the process of landslide and earth flow. They are also the markers of a turning point in the geologic history of the west.

The connecting ridges between the volcanic plugs consist of various rock types from the Franciscan Formation. The most impressive is the narrow ridge of serpentinite between Hollister Peak and Cerro Romauldo, and some similar serpentinite ridge spurs at the eastern edge of the chain. The serpentinite hills are conspicuously bare of vegetation, a product of the lack of certain chemical elements in serpentinite soils. The strange chemistry born of the metamorphic processes that converted peridotite like igneous rocks to serpentinite, also has produced a number of rare plants. The peridotite is thought to have once been the base of oceanic crust that smashed into the subduction zone. Other common rock types are redrock and basalt, the former being a decomposed variety of the latter.

The unique nature of these peaks was first noted in the scientific literature in 1904 by H.W. Fairbanks, who made an intensive study of the geological history of the area, said.

"As scenic features these buttes are very interesting. They have no counterpart in the Coastal Ranges. They are interesting to the students of petrography also, as their characteristics are uncommon."
H.W. Fairbanks, 1904

This series of buttes constitutes the most striking topographic feature of the quadrangle. There are about 12 and they range in altitude from 400 to 1600 feet. Many of them are almost completely isolated and rise from the open valleys with bold and frequently precipitous rock faces. Morro Rock, the most northerly of these buttes, rises from the ocean as a bare rounded mass of rock nearly 600 feet, forming the most striking scenic feature of the coast of California..."

H.W. Fairbanks, 1904
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Wildlife and Vegetation

The chain of hills provides both habitat and a wildlife corridor that is vital for the continued viability of animal populations in the area. Each peak has a different mix of bare rock, grassland, oak woodland, and chaparral that provide a wide range of habitats. Nesting sites for both terrestrial and marine birds abound on the hills and in the flanking riparian forest. The Audubon Society estimates that there are about 100 species of birds that breed in the area, which is in the top five of the 1,000 areas of the nation for the winter bird count. Of particular note is a Peregrine Falcon nesting site on Morro Rock, and a colony of Black Shouldered Kites on the flanges of Hollister Peak. Deer, bobcat, coyote, and many small mammals abound. Reptiles and amphibians include the Western Pond Turtle, Red Legged Frog, and Two-Stripped Garter Snake.

Plant communities include lichen, seaweed around the rock, sea-spray wetted rock communities on Morro Rock, coastal sage scrub, central dune scrub, Monterey Pine woodland and eucalyptus on Black Hill, and on the other hills coast live oak woodland, annual grassland, mixed evergreen woodland coastal sage scrub and central maritime chaparral. Bare rock slopes, rich in algae and specialists plants such as Dudleya are found near the top of each mountain. The ridges between the mountain carry populations of rare manzanitas, rare plants that live on serpentinite, and a rich variety of wildflowers. Rare or endangered plants include the Jones Layia, the Maritime Sanicle, the Adobe Sanicle, Betty's Dudleya, the San Luis Obispo Nodding Thistle and several other plants. The valleys which border the hills contain some relatively pristine riparian willow and riparian sycamore communities, and there are several farm ponds with their associated, but not uncommon, plant species.

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Topology and Hydrology

The volcanic plugs tend to have very steep sides of exposed rock, although buttresses slope from these peaks to make all of them accessible. The steep slopes are popular with mountain climbers, while formal or informal trails make their way up the buttresses or summits of most of the hills. The slopes can be divided into halves, the upper 700 feet being very steep and dominated in most cases by exposed rock, and the lower 600 feet by grass, chaparral, or oak woodland that is mainly used as steep range land of less than 20% slope. In places these more gentle slopes are covered by boulder fields derived from giant landslides which were derived from the steep volcanic slopes. These create a unique landscape.

The peaks are flanked by two deep valleys. The western end of the chain of hills is flanked by the Los Osos Valley on the south, and Chorro Creek on the north. The creeks both flow westward toward Morro Bay. In the central part of the chain a divide crosses both valleys, both to the north and to the south, so that waters along the eastern end of the chain flow into San Luis Obispo Creek and discharge into San Luis Bay. The City of San Luis Obispo lies along the flatlands of San Luis Obispo Creek. The chain of hills forms the dominant scenic backdrop to nearly all parts of the city. The serpentinite ridge that extends southeast from Cerro San Luis Mountain is flanked on the south side by the wetlands of Laguna Lake, much of which is preserved by the City as a wildlife preserve.

The flow of water in the aforementioned creeks is usually seasonal, with portions being dry for a few months every year. Chorro Creek often flows year round, but Los Osos Creek, Warden Creek and the headwaters of San Luis Creek are ephemeral streams. There are no year round streams born on the chain of hills, although freshets occur in the rainy season. The seaward end of both Chorro Creek and Los Osos Creek contain healthy riparian wild forest. These creeks are subject to intensive management planning which includes both ecological restoration and control of sediment flow into Morro Bay. Restoration will, in part, require the establishment of more natural conditions in sections of those creeks much altered by agricultural development.

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The Nine Sister themselves have not been explored in detail for Archaeological evidence. However, the Chorro Valley which surrounds the Morros has several hundred Chumash Indian mortar sites. Chorro Valley was heavily occupied by the Chumash Indians. With this information, it can be assumed that the Chumash used the Morros as well.

A June 1992 records check with the California Archaeological information Center (UCSB) confirmed that mortar sites exist throughout the high meadows of Bishop Peak.

A 1977 field check (Charles Dills) found "marginal aboriginal evidence," on Bishop Peak including three stone fragments that may have been scrapers, a small mortar in the area of a city park on Patricia Drive, and a larger mortar site uphill near the Highland Drive summit.

Black Hill, Turtle Rock and the area around Hollister Peak also has Chumash sites but have not been investigated in detail.

The Northern Chumash Council has indicated that the Morros are sacred to the Chumash, and Bishop Peak occupies an area which is considered significant.

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Periodically from 1891 to 1968 quarrying occurred at Morro Rock and Bishop Peak. Some gravel quarrying still occurs on the lower slopes of Bishop Peak. However, to prevent further quarrying and defacing of Morro Rock concerned citizens, on February 15, 1968, succeeded in obtaining its designation as State Historical Landmark #821.

In more recent years applications for quarrying permits on Cerro Romauldo and Chumash Peaks have been turned down by the Board of Supervisors. However, continued blasting of rock by the Corps of Engineers, resulted in a state policy resolution which determined Morro Rock should be established as a Natural Preserve in accordance with Criteria for Natural Preserves as recommended by the State Park and Recreation Commission. In September of 1969 Congress transferred full title of Morro Rock to the State of California to terminate damaging quarrying activities.

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History of the Nine Sisters

The geologic make up of the Morros are very important. However, the people of San Luis Obispo County value them for their historic value as well. The sections to follow give brief history of the volcanic peaks we have all grown to appreciate.

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Morro Rock

Morro Rock, at 576 feet, is the northern most visible member of the Nine Sisters. It is probably the most photographed of all the Morros, and provides a unique outcropping to the entrance of Morro Bay.

Morro Rock has been an important mariner's navigational landfall for over 300 years. It was chronicled in the diaries of Portola, Fr. Creaspi and Costanso in 1769 when they camped near this area on their trek to find Monterey. Sometimes called the Gibraltor of the Pacific, it is the last in the famous chain of nine peaks which extends from the City of San Luis Obispo. Morro Rock was first sighted in 1542 by Juan Rodriguez Cabrillo who named it "El Morro". In Spanish "Morro" means crown shaped hill.

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.

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Black Hill

Black Hill, with an elevation of 665 feet, is located in Morro Bay State Park. It is rumored Black Hill got its name from a tar seep on the north side of the hill.

Many years ago, John Fleming, former parks superintendent, was working on several conservation projects planting Penny Pines. To make sure he had enough pines to do the job, he ordered twice as many as required, fearing he would only receive half of what he needed. When the pines were delivered, he received all he had ordered. The extra pines were planted on Black Hill, creating Fleming's Forest. The pines have since spread to nearby Turtle Rock, creating a wonderful habitat for many bird species and owls.

Today Black Hill is used by many people, including residents of San Luis Obispo County, tourists, the Morro Bay Natural History Association for nature walks, and the Sierra Club. Black Hill provides an overlook to the City of Morro Bay and gateway to the Nine Sisters.

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Cabrillo Peak

Cerro Cabrillo is the third visible volcanic cone, or butte, southeast of Morro Rock. It is located within the section of Morro Bay State Park bordered by Turri Road, South Bay Boulevard and Chorro Creek.

Cerro Cabrillo's elevation is 911 feet and provides a moderately strenuous hike with some truly delightful views of the Morro Bay Estuary and the remaining chain of the Nine Sisters. It was named by Mrs. Louisiana Clayton Dart in 1964 in honor of the famous Portuguese explorer, Juan Rodriquez Cabrillo, sailing for the Spanish crown, who was known to be in the vicinity in 1542.

Although Cerro Cabrillo lacks the magnificent rugged appearance of its neighbor, Hollister Peak, it does boast a rock formation on its east flank called a "tiki", resembling the Polynesian carvings of mythological figures found on many Pacific Ocean Islands. Outcroppings can be seen from the trail off South Bay Boulevard or from the Elfin Forest trailhead. Cerro Cabrillo is often covered with a bountiful array of wildflowers, among these you will find pink genetian, deerweed, fairy lanterns, soap plant, mallow, yellow and chocolate mariposa lilies, Indian pink, owl clover, pearly everlasting, golden stars, sticky monkey flower and hummingbird sage.

The Cabrillo Peak Area is currently owned and operated by the State Park System. Many local volunteer groups aid the park officials with the maintenance, cleanup and building of trails.

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Hollister Peak

Hollister Peak Viewed from Highway 1
Hollister Peak Viewed From Highway 1

Hollister Peak was inhabited by the Chumash Indians when Father Junipero Serra established the Mission San Luis Obispo de Tolsa in 1772. After the Mexican revolt in 1822, the mission lands were secularized and divided among preferred Mexican citizens.

The rancho encompassing Hollister Peak was called Rancho San Luisito and was granted to Judge Jose Guadalupe Cantua in 1841.  Guadalupe Cantua added on to the San Luisito Adobe in 1841 and portions of the adobe still stand on the Cuesta College campus. It is now known as the Hollister Adobe as the Joseph Hollister family moved to this ranch and into the adobe in 1866.

At that time the spectacular mountain was known as Cerro Alto or High Mountain. It has also been known as the Morro Twin. In 1884 the U.S. Coast and Geological Survey named it Hollister Peak for the family who lived at the base of the mountain. Three generations of the Hollister family were raised in the old expanded ranch house until financial difficulties in 1907 required the sale of portions of the ranch. The Hollister family continued to own property at the base of the peak until the 1950's or 60's.

The Canet family were also long time property owners and residents on the land around Hollister Peak. The Canet family cemetery is still situated on the property. The 50 graves represent many generations of the Canet family.

Before the turn of the century a Swiss immigrant, Battista Tomasini bought land on the northern half of Hollister Peak. It was later farmed by his grandson Warren. When Warren Tomasini was killed in the 1965 wreck of the ocean liner Yarmouth Castle, his brother Homer A. Tomasini took over the operation. He remains the owner today.

In the 1970's P.G.E. built some huge transmission line towers along the south eastern foothills which adjoin Hollister. Recently a new owner, J.

Hammons of Missouri, submitted a development plan for the property along Highway 1 and in the lower foothills of Hollister Peak. The plan calls for a golf course, motels, restaurants, and convention center. There was much opposition expressed by the local citizens and the plan was rejected by the Board of Supervisors.

In the late 1990s 576 acres of Hollister Peak was purchased by the Buckingham Family, which includes the portion of Hollister Peak's back side adjoining Morro Bay State Park.

Hollister Peak is not open to the public to climbing, or hiking of any kind. There has been several discussions as to what uses the peak could serve. It has been thought by many that this peak should remain undisturbed as an ecological reserve, and just to admire as it is.

Hollister Peak remains a majestic masterpiece created by mother nature. It often looks like a dinosaur as it towers 1,404 feet above the ocean. As quoted by the H.W. Fairbanks, Description of the San Luis Quadrangle, 1904.

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Cerro Romauldo

Cerro Romauldo, at elevation 1,306 feet, was named after the only Chumash Indian to receive a Mexican Land Grant of 117 acres following the secularization of the missions. Romauldo called it "Huerta de Romauldo", Romauldo's kitchen garden or orchard. Romauldo sold his land to Captain John Wilson, owner of the 32,622 acre ranch Canada de los Osso y Pecho y Islay Rancho, in 1846. Rock from Cerro Romauldo was used for building material for the Southern Pacific Railroad in the 1890's.

Today the north side of Cerro Romauldo, adjacent to Highway 1, is owned by the State of California. The California National Guard uses it for fitness training.

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Chumash Peak

Chumash Peak, at elevation 1257 feet, was not named until 1964, when Mrs. Louisiana Dart, curator of the San Luis Obispo County Museum, played an instrumental role in filing papers with the U.S. Department of the Interior for officially naming it in honor of the Chumash Indians who lived in San Luis Obispo and Los Osos area and built the mission.

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Bishop Peak

Bishop Peak
Bishop Peak Viewed from Stenner Creek Road

Bishop Peak the highest of all the peaks, rises 1,559 feet above the sea. The rocky outcroppings makes it one of the most distinguishable of all the peaks. John Muir, founder of the Sierra Club, made a note in his travel diary while descending from Cuesta Grade.

Bishop Peak was named by the padres at Mission San Luis Obispo because of the three sharp points on the summit.

The peak was mined heavily in the late 1800s and early 1900s. The Pacific Coast Company built a narrow gauge railway to its base to transport material to neighboring sites. The railway had no engines to pull the mine cars up and down the tracks. Instead they used a pulley system. The weight of the full cars easily pulled up the empty cars to the quarry site. Rock from Bishop Peak was used to build many structures in the City of San Luis Obispo. Mining continued until about 1935, and resumed again in 1979.

This peak has become a special part of San Luis Obispo county. In 1976 the City of San Luis Obispo had a chance to make Bishop Peak a permanent fixture when a 450 acre ranch came up for sale. But unfortunately, the City decided not to buy the parcel because more pressing projects needed financing.

Today, Bishop Peak is used heavily by many hikers and rock climbers. A recent acquisition of 108-acres by the City of San Luis Obispo in March 1998 and two other acquisitions from the Gnesa Family in 1992 and the Ferrini Family in 1995 has created the 350 acre Bishop Peak Natural Reserve which protects the upper portions of the Peak in perpetuity. But unfortunately, the remainder of the Bunnell Ranch will be developed.

New hiking trails have been completed allowing greater exploration of the Bishop Peak Area, and a view from the top of the Peak itself. These hiking trails will help protect the remainder of the peak from overuse.

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Cerro San Luis (San Luis Mountain)

Cerro San Luis Mountain
San Luis Mountain viewed from the Cal Poly Campus

Cerro San Luis, with an elevation of 1,292 feet, is in the heart of the City of San Luis Obispo. It is the mountain most residents of San Luis Obispo are attached to. The quotes by Myron Graham, San Luis Obispo City Councilman , 1975, and Richard J. Kresja, San Luis Obispo County Board of Supervisors, 1979, illustrate this.

Cerro San Luis is currently owned and operated mostly by the Madonna Family. This family's generosity concerning access and use has been widely accepted and appreciated by the community.

In October 1996, the City of San Luis Obispo acquired another 75 acres from the Maino Family on San Luis Mountain adjacent to and additional 40 acre parcel. We can now visit the old lemon grove near the "M" on the mountain. The "M" is for Mission High School.

As a side note the City of San Luis Obispo used to own San Luis Mountain, then sold it to the Madonna Family in the late 1950's or early 1960's

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Islay Hill

Islay Hill is the southern-most volcanic cone located near the county airport. The general character of the area is rural. Islay is a round grassy hill that rises to an elevation of 777 feet. The lack of visible outcroppings distinguishes Islay Hill from the other peaks. Islay Hill is visible for at least one mile in all directions, making it an important city landmark and greenbelt. The name "Islay": is derived from an Indian word meaning wild cherry. A lieutenant who accompanied Portola in this area in 1769 referred to it as "Yslay" in his journal.

Islay was part of the 31,000 acre Corral de Piedra land grant. The Rodriquez Adobe, constructed in 1858, remains near the base of the hill. Islay Hill has lost much of its character with the addition of a 500 unit subdivision at the base of the mountain. Islay Hill Park which used to have Islay Hill as a beautiful backdrop will soon be blocked by additional homes between the park and the Islay Hill. This is a poor example of planning as it was decided not to use the natural creek boundaries between the development and Islay Hill to protect most of the character of the mountain. Wildlife access to the creek has been greatly impacted with this decision. The 350 foot elevation limit for development on the west side was not enough to preserve the wildlife habitat of the area.

Davidson Seamount

Davidson Seamount is located 75 miles west of San Simeon. It stands at 7,800 feet above the ocean floor and 3,600 feet below the surface of the water. It was named after George Davidson a leading scientist in the fields of geodesy study and geography who participated in the first official study of the Pacific Coast. This is also the first time the word "seamount" was used to describe an underwater feature. It was once thought that Davidson Seamount was part of the Morros Chain but in the late 1990s David Clague, a geologist with the Monterey Bay Aquarium Research Institute, said the Morros and the Seamount were not created during the same period of intense volcanic activity. Davidson Seamount, at eight miles wide and 26 miles long, is much larger than any of the Morros and was created as a result of multiple volcanic eruptions that built up the sea floor.

For more information on Davidson Seamount Check out these links

Recent Press Releases

A mountain of exotic sea life
Seamount may be added to marine sanctuary
David Sneed
The Tribune, June 14, 2004

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Hiking Trails on the Nine Sisters

Most of the Nine Sisters (Morros) are privately owned. In recent years, Bishop Peak and San Luis Mountain have become more accessible due to the efforts of many individual, landowners, public and private organizations.

In the coming years the Morros Advisory Committee, Sierra Club, landowners, and public and private agencies are working to create a Morros Master Plan. This Plan will designate more recreational areas on the Nine Sisters Chain, yet work to preserve the character we have all grown to love and enjoy.

Below are the peaks which can be accessed by the public.In any event below are the limited recreational areas located in the Morros Chain.

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Additional Reading About the Nine Sisters (The Morros)

Brewster, Jerry and Varner, James. Morro Peaks/Open Space Study. Advisor Andrew Merriam, California Polytechnic State University at San Luis Obispo, California. March, 1973.

Chipping, David H. The Geology of San Luis Obispo County. California Polytechnic State University, 1987.

City of San Luis Obispo Planning Department. Administrative Draft Open Space Workbook. May 7, 1992.

Dart, Louisiana Clayton. Vignettes of History in San Luis Obispo County. 1978.

Department of Geology. Geology and Petrology of the Cambria Felsite, a New Oligocene Formation, West-Central California Coast Ranges. Enrst, W.G. and Hall, C. A., Jr., University of California at Los Angeles. April, 1974.

Dickerson, Sharon Lewis. Mountains of Fire - San Luis Obispo County's Nine Sisters. San Luis Obispo. EZ Nature Books, 1990.

Fairbanks, H.W. Description of the San Luis Obispo Quadrangle, California: Geologic Atlas. San Luis Folio 101, United States Geological Survey, 1904.

Graham, Priscilla M. The Preservation of San Luis Obispo's Unique Scenic Asset — The Nine Peaks. Senior Project Report, California Polytechnic State University at San Luis Obispo, California. 1971, .

Gonnella B., editor. Trail of the Morros. For California Polytechnic State University at San Luis Obispo, class - Park Planning Management. Professor E.W. Conner. June, 1972

Havelik, Neil. A Look at Hollister Peak. San Luis Obispo Chapter of Native Plant Society. 1971.

Hood, Leslie Editor. Inventory of California Natural Areas. California Natural Areas Coordinating Council. Copyright 1975-80 and 1982.

Rodin, Dr. Robert J. Evaluation of the Nipomo Dunes and Point Sal Areas for A Survey of the Natural History for the National Park Service for Registered Natural Landmark Designation. August, 1972.

San Luis Obispo County Planning Department. A Specific Plan for the Preservation of the Morros. December, 1972

San Luis Obispo County. Natural Areas Plan. 1992

Strong F. and Associates. A Specific Plan for the Morros. 1973

Wiley, Jane. The Seven Sisters. Office of Education, San Luis Obispo County. 1966.

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