Sweeney Ridge became part of the Golden Gate National Recreation Area (GGNRA) in 1984. GGNRA is an urban part of the National Park System extending from Marin to San Mateo Counties. It provides open space near urban areas so people can take short breaks from our technologic society to "climb the mountains and get their good tidings."

Sweeney Ridge Trails
Daytime temperatures can range from the upper 20s (°F) in January to 100°F in September. Fog is common during the summer months.

Always bring a jacket as a warm clear day can change abruptly when the fog blows in from the Ocean.

The Sweeney Ridge Trail follows routes used by the Coast Guard and personnel using a radar tracking station. The radar station was part of a NIKE missile installation. The NIKE missile silos can be seen at Milagra Ridge to the north of Sharp Park Blvd.

How to get there: These trails lead to Sweeney Ridge Trail and the Portolá Discovery Site Monument. Look at the topographic profiles to pick the one that is right for you. There are three trails to the Portolá Discovery Site:

A Brief History
Pruristac was a small village of 30 to 50 Ohlone Indians in the San Pedro Valley prior to the coming of the Spaniards in 1769. These peaceful, hunter-gatherers lived off the plentiful plants, fish, and small game of San Pedro Valley. They had neither metal nor pottery. Shells, bones, wood, and rock were fashioned for tools and weapons were tipped with chert. An epidemic decimated the local Indian population in 1792. An 1828 census lists just 16 Indian inhabitants.

Rancho San Pédro y San Pablo was established in San Pedro Valley in 1786 to provide grain and livestock for Mission San Francisco de Asís (Dolores).

Sweeney Ridge was once part of the 9000­acre Mexican land grant to Francisco M. Sánchez in 1839. Sánchez's Rancho San Pédro was owned by his family after his death (1862) until the 1870s.

There is still dispute as to why the area is called Sweeney Ridge. Who was Mr. Sweeney? Was there such a being at all? And only this is certain: nobody knows. Edwin Sweeney may have run cattle there back in the 19th century. Or Sweeney may have been a Mission Street butcher. More intriguing still is the explanation that the name might have been "Feeney." Or perhaps it was "sweeny," an equine word which may have been applied to the shape of the ridge itself.

Portolá Discovery Site (A view from the top)
In July 1769 Portolá led 63 men and 200 horses overland from San Diego to rediscover Monterey. But, so poorly had it been reported, Portolá failed to recognize the place and his expedition continued north. Late in October, exhausted, hungry, and sick, the men advanced along the coast into what is today San Mateo County. The actual moment of the original sighting of San Francisco Bay probably went unrecorded. It was believed to have been sighted late in October by Sgt. Jose Francisco Ortega, one of Portolá's scouts.

Nov. 4, 1769 is the symbolic discovery date agreed to by the Portolá Expedition Bicentennial Foundation. Seems on that day Capt. Portolá and the entire party climbed Sweeney Ridge and beheld the bay. Portolá, who never showed much relish for exploration and whose logs reveal he was abysmally ignorant about the importance of the discovery, was disappointed with the find.

The precise location from which Portolá beheld the bay was much debated well into this century. Most now accept Sweeney Ridge.

Geology
Sweeney Ridge is located east of the inactive Pilarcitos Fault and immediately west of the San Andreas which is the major active earthquake fault in North America. Over millions of years each fault has slipped repeatedly, crushing and grinding the rocks which now form the valleys of San Pedro Creek and Crystal Springs Reservoirs. In addition, there are several smaller branch fractures between these major breaks which created the intervening valleys. Movement along these faults has broken off the rocks of Sweeney Ridge from the rest of North America. The rocks of Sweeney Ridge slide northwesterly, at a rate of between one and two inches per year, toward Alaska.

On the lower part of the ridge, the rocks are highly shattered because of their proximity to the fault. Often these rocks are covered by an assortment of broken fragments, including mud, sand, and angular pebbles. This "slope wash" has been carried down from higher elevations by rain and gravity. There are some scattered outcroppings of relatively solid rock along the ridge.

The rocks are part of the Franciscan Formation and are about 100 million years old. This area was once covered by the ocean and evidence of submarine volcanism can be found to the north and south of this area.

The primary rock seen in most locations is sandstone. Often called graywacke, it ranges from light tan to dark gray. It is easy to identify from a freshly broken surface because it looks and feels like coarse sandpaper.

Shale is present in some places. It tends to break easily into many small, flaky pieces which do not have the gritty feel of sandstone. The shales are often interlayered with chert, a harder rock, usually reddish­brown in color in this area, which breaks into large blocky chunks.

The most difficult of all the rocks to identify is basalt. Basalt is the type of lava extruded during eruptions of Hawaiian volcanoes. Here it is very old and decomposed. It usually looks more like a hardened mudstone. Some basalt is evident near the radar tracking station.

Vegetation
Vegetation in this area is called the coastal scrub plant community. Coastal scrub plants are evergreen shrubs and exhibit adaptations to dry summers. The most abundant plant along the trail and visible on the hills is coyote brush. Its bushy appearance, woody stems, and small, leathery leaves prevent water loss. In the spring and fall, small whitish flowers are visible.

Coastal sagebrush is intermingled with the coyote brush. Sagebrush leaves are branched into linear filaments. When crushed, the grayish­green leaves give off the pungent smell of sage. This plant becomes dormant during summer droughts.

Contributors
Beverly Baldwin

Richard Lambert

Lotus Perez

Michael Svanevik

The Pacific Raptor Report

The Wilderness World of John Muir (Houghton Mifflin Co.)

 

C. L. Case. Sweeney Ridge Hiking Trails. First edition, 1989. Second edition, 1998. Published by Skyline College.

All photos in ../sweeneyridge/ ©CLCase