San Bruno Mountain

Topographic rendering done in 1869 showing trees in the ravines

The name "San Bruno Mountains" appears on the land-map of Rancho Cañada de Guadalupe drawn by Jean Jacques Vioget (presently in the collections of the Bancroft Library, University of California, Berkeley) some time in the 1840s.[5] The name was continued in use by the Geological Survey of California in 1865, which described the place as a short range extending from Sierra Point nearly to the Pacific Ocean.

It is a part of the Franciscan Formation of diverse types of rocks laid down in the Mesozoic, then uplifted as fault-blocks starting in the Pleistocene;[6] the uplift occurred before the initial occurrence of the San Andreas transform-fault.[7] Present-day San Francisco is at the center of the formation and is composed of smaller northwest-trending ranges extending up into Marin County. The mountain itself actually consists of two parallel northwest trending ranges separated by the Guadalupe Valley. These two ranges are united by a saddle at the northern end of Colma Canyon. The northernmost range attains a peak of 850 feet (259 m), while the southern range rises abruptly from Merced Valley at the south to reach the 1,319 feet (402 m) Radio peak in a horizontal distance of only 0.8 miles (1.3 km). Slightly to the east of the highest peak, and south of the main range, a small block reaches 581 feet (177 m) in South San Francisco. This southern range is often referred to as San Bruno Mountain, the northern range is sometimes called the Crocker Hills, and the small southern hill is called Sign Hill because of large concrete letters emplaced by the city of South San Francisco. In the 1850s San Francisco Bay still lapped against the eastern sandstone cliff flank of San Bruno Mountain, but today the entire shoreline is bay fill.[8]

The region is drained by two major streams: Guadalupe Valley Creek flowing through Guadalupe Valley, and reaching the Bay north of Brisbane. Colma Creek rises from a source in San Bruno Mountain State and County Park and runs west into the deep cleft of Colma Canyon; it then turns southeast and runs along the valley south of the mountain (fed by Twelve-Mile Creek and at least eight other nameless streams) until it reaches the San Francisco Bay just north of San Francisco International Airport.[9] Formerly, steelhead trout swam almost to the headwaters of Colma Creek to spawn; boats used to travel up to what is now Molloy's Tavern on Old Mission Road.[10]

Fog rolling over San Bruno Mountain near the central radio/television antennae.

These two mountains are underlain primarily with late Cretaceous dark greenish-gray graywacke, a poorly sorted sandstone containing angular rock fragments, about ten percent feldspar and detrital chert. The angular unsorted content implies a rapid erosion and burial in a depositional basin, with an outcome of few fossils. Exposed graywacke can be observed on high ridges and on the steep canyon walls. Radiolarian chert is exposed on certain south facing slopes of San Bruno Mountain and at Point San Bruno. The most important rock type is serpentine, a greenish soft material that is the California State Rock. Outcrops of this rock are found near Serbian Ravine and at Point San Bruno. Serpentine's importance is its unusual and diverse mineral composition which imparts to associate soils the ability to host rare plants, not usually supported on common soils. San Bruno Mountain is consequently a habitat for a variety of uncommon plants, which in turn host even rarer animal life. Another unusual feature is an inland sand-dune (Colma formartion) on the western slope (behind Daly City's John F. Kennedy Middle School), more than two-and-a-half miles from the ocean.

Since the climate is dominated by marine air flow, temperatures are milder in the winter and summer on these mountains. Furthermore, summer temperatures are further reduced by the annual appearance of marine fog enshrouding the mountains most mornings between late June and late August; this fog is particularly pronounced on the western slopes. Minimum credible temperature might extend as low as 20 °F (−7 °C) in the sheltered valleys. Winds are higher than on reference locations at surrounding points; in fact, on ridges it is not uncommon for the most fierce winter storms to produce gusts from 50 to 80 miles per hour (80 to 129 km/h). Precipitation is similar to surrounding cities, or about 22 inches (560 mm) per-annum, with approximately 66 days-per-annum realizing perceptible rain. On several occasions the mountain has been temporarily covered by snow, including December 1932, January 1952, January 1957, January 1962, February 5, 1976, February 26, 2011, and February 5, 2019.

The Portola expedition visited San Francisco Bay in 1769. The expedition is usually considered the first European presence in the area. Five years later Fernando Rivera and four soldiers climbed the mountain and watched sunrise across the bay. The mountain was named by Bruno de Heceta for his patron saint.

Aerial view of San Bruno Mountain from the east. The buildings on the mountainside on the right are part of Brisbane.

San Bruno Mountain includes portions of five Mexican land grants; the southernmost being Rancho Buri Buri. Jose Antonio Sanchez, who rode by mule as a child from Sonora, was given Rancho Buri Buri in 1827, with confirmation in 1835. Rancho Buri Buri extended from the bay salt flats to San Andreas Valley and from Colma to Burlingame. Rancho Canada de Guadalupe la Visitacion y Rodeo Viejo contained most of the present day San Bruno Mountain; this rancho contains the city of Brisbane, Guadalupe Valley, Crocker Industrial Park, Visitacion Valley and the old rodeo grounds by Islais Creek. In 1835 this rancho was granted to Jacob P. Leese. In 1884 banker Charles Crocker acquired core holdings of this rancho amounting to 3,997 acres (1,618 ha) from Leese's successors, and that land devolved to the Crocker Estate Company, who are the present day owners of San Bruno Mountain. Three other ranchos held minor portions of the northern flank of San Bruno Mountain.

The southern border of San Francisco runs along the base of the northern hillside, with Daly City encircling the north side of the mountain. Brisbane is on an eastern prominence, and the cemeteries of Colma and the community of South San Francisco along the south. The 144-acre Guadalupe quarry on the south side of Guadalupe Canyon is presently owned and operated by American Rock and Asphalt, Inc.,[11] while the Crocker Industrial Park occupies much of the canyon floor. Reputedly, an exploratory gold mine exists on the mountain.[12]

KRON (Channel 4) was the first television station to place a transmitter tower on Radio Peak, in 1949, followed by KQED and KTVU, though these tenants moved their transmitters to Sutro Tower in the 1970s. A number of FM stations built transmitter towers on the mountain, and in 2005, KNTV moved its transmitter to the mountain, on the former KCSM-TV tower. KTSF occupied the former KRON site until 2018, when it entered into a channel sharing agreement with KDTV-DT and moved to its site on Mount Allison.

Nossaman attorney Robert D. Thornton pioneered the Habitat Conservation Plan (HCP) concept creating the first such plan for the area around San Bruno Mountain.

Undeveloped portions of the mountain that sit between the state park and the counties of San Mateo and San Francisco are still privately owned and at risk for development. Examples of these locations include the prehistoric sand dunes above Hillside Park in Daly City, and the eucalyptus groves bordering the Crocker and Southern Hills neighborhoods of Daly City. These areas are of great ecological significance, hosting the same plant and animal communities as found in the state park.

Westbay controversy

Guadalupe Canyon Parkway from the south

In 1965, Westbay Community Associates announced a plan to level a portion of the mountain to fill 27 square miles (70 km²) of San Francisco Bay north of Sierra Point with landfill. The proposal intended to create housing developments in the "Saddle" just north of Guadalupe Canyon Parkway and in the landfill zone.

In order to remove 250 million cubic yards (190,000,000 m³) of earth from the ridge, Westbay proposed using a conveyor belt system to transport the fill across Bayshore Boulevard and Bayshore Freeway to offshore barges, which would then deposit the material along the shores of the Bay.[13]

Opposition by organizations such as Save The Bay[14] and the residents of Brisbane led to the defeat of Westbay's conveyor plan in June 1967 and the ceasing of all landfill operations at Sierra Point by December 1972.[13]

Terra Bay development

Terra Bay Phase II (Mandalay Towers condominium, rear center) and Phase III (Centennial Towers, south tower, rear right) at the base of San Bruno Mountain

The Terra Bay project was approved in the mid-1980s for development at the south and southeast base of San Bruno Mountain.[15] Terra Bay was constructed in three phases: the first phase constructed townhomes and detached houses; the second phase constructed more housing units, including the one of the tallest buildings in South San Francisco,[16] a condominium tower named the Peninsula Mandalay, and the third phase constructed an office building named Centennial Towers.[17] The original developer, W.W. Dean & Associates, was unable to complete the project, and SunChase Holdings acquired the project in 1992, completing site preparation before selling the parcels for Phase I to Centex Homes.[18]

The Terra Bay site was known to include habitat for the Mission blue and Callippe silverspot butterflies; the original developer received a US$15,000 (equivalent to $41,000 in 2021) fine in 1983 for bulldozing part of the habitat during site preparation.[19] Under the terms established by the 1982 amendment to the Endangered Species Act, the nation's first-ever Habitat Conservation Plan (HCP) was agreed upon, allowing developers to destroy the habitat of endangered species if substitute lands were made available.[20] SunChase agreed to fund ecological restoration to mitigate the impact of Terra Bay during the development of Phase I under the terms of the San Bruno HCP.[21] SunChase entered a joint venture with Myers Development for the development of Phases II and III;[18] although Phase III had 20 acres (8.1 ha) of land available for construction, the completed Centennial Towers was scaled back to fit on just 8 acres (3.2 ha),[22] partly in order to establish a buffer zone between the development and an ancient shellmound.

Centennial Towers (south tower, shown, completed in 2009; north tower delayed) was originally named Mandalay Terrace during the planning of Terra Bay Phase III.

Although the shellmound had been noted as early as 1909,[23] a sample of 22 cubic metres (780 cu ft) of the shellmound conducted in 1989 by Holman & Associates (commissioned by W.W. Dean) revealed the massive shellmound contained human remains, and further, that the shellmound site is eligible for nomination to the National Register of Historic Places.[24] The Holman & Associates report was not made public for nearly ten years,[25] with leaked copies circulating privately in 1997, and a public copy incorporated in the draft Environmental Impact Report in 1998.[24] A lawsuit was settled out of court, resulting in the developer selling the land which included the shellmound and habitat for the Mission blue and Callippe silverspot butterflies to The Trust for Public Land,[26] who would incorporate the parcel into San Bruno Mountain State Park. Ultimately, Terra Bay Phase III was scaled back significantly from the original mixed-use retail/office proposal.[27][28] The shorter 12-story south tower was completed in 2009,[29][30] and the taller 21-story north tower is scheduled for completion at the end of 2016.[31]

There are a variety of habitats in this mountainous area, and notably the following rare or endangered flora:

• Coast rock cress (Arabis blepharophylla)
• Franciscan Wallflower (Erysimum franciscanum)
• Montara Manzanita (Arctostaphylos montaraensis)
• Pacifica Manzanita (Arctostaphylos pacifica)
• San Bruno Mountain Manzanita (Arctostaphylos imbricata)
• San Francisco Campion (Silene verecunda)
• San Francisco Owl's Clover (Orthocarpus floribundus)

• San Bruno Mountain State Park
• Mission blue butterfly
• Mission blue butterfly habitat conservation
• San Bruno elfin butterfly
• United Airlines Flight 863
• List of summits of the San Francisco Bay Area
• List of California state parks

Wikimedia Commons has media related to San Bruno Mountain.

• "San Bruno Mountain". Geographic Names Information System. United States Geological Survey. Retrieved 2009-08-24.
• Environmental Services Agency of San Mateo County, information on history, trails, park map, activities, park hours.
• San Bruno Mountain State Park
• San Bruno Mountain Watch, whose mission is to preserve San Bruno Mountain's Native American village sites and endangered habitats.
• Trailspotting: Hiking San Bruno Mountain Description, Photos and GPS/mapping data
• Climate Survey of San Bruno Mountain, prepared for Crocker Land Company by Metronics Associates, Palo Alto, Ca., October 20, 1967
• Elizabeth McClintock and Walter Knight, A Flora of the San Bruno Mountains, San Mateo County, California, Proceedings of the California Academy of Sciences, Fourth Series, Volume XXXII, no. 20, pp. 587–677, November 29, 1968
• J.D. Whitney, Geological Survey of California (1865)
• John Hunter Thomas, A Flora of the Santa Cruz Mountains (1960)