San Bruno Mountain is a rugged 2,416-acre park located at the northern end of San Mateo County. It is geologically different from the rest of the county and from Marin, which gives it unique plants. This ecologically significant island is surrounded by urbanization: the communities of Daly City, South San Francisco, Brisbane and Colma, and is very close to the southern edge of San Francisco. The Mountain’s 4-mile long ridgeline runs southeast to northwest and its highest point is Radio Peak (1,314 feet), which is home to several radio broadcast towers.
Hiking is the most popular activity in the park, which, on a clear day, offers stunning views of San Francisco and the surrounding Bay Area, including Mt. Tamalpais, Mt. Diablo and the Farallon Islands. San Bruno Mountain is home to a wide variety of rare and endangered plant species, with six plants that grow nowhere else in the world. There are also three rare and endangered butterfly species, one of which is found nowhere else in the world.
San Bruno Mountain is both a state and county park and is notable as the site of the nation’s first Habitat Conservation Plan. An HCP is a conservation strategy that allows limited development in exchange for financial support for preservation of threatened species and their habitat.
Weather can be unpredictable on San Bruno Mountain. Fog can be present year-round and so can midwinter sunshine. Winds along the ridge can reach 30 mph, so be prepared by dressing in layers. This distinct botanical region is known as the Franciscan Landscape and it supports a diversity of plants and wildflowers that set it apart from other California coastal areas. It once extended from San Bruno Mountain, north to the Golden Gate. Then, in a span of 160 years, the majority of this remarkable collection of plants was paved over to create the city of San Francisco and surrounding communities.
Now, all that is left of this special landscape is on San Bruno Mountain itself. San Bruno Mountain’s varied topography and proximity to the Pacific Ocean and San Francisco Bay offer the perfect setting for microclimates, which in turn support many discrete habitats.
On the western slope in Daly City, an inland sand dune is a last reminder of a larger Pacific Ocean. Two streams, the Guadalupe Valley Creek and Colma Creek, drain the mountain, and their riparian corridors support a variety of native wetland plant species that provide habitat for migrating birds.
The variety of uncommon plants found on the mountain host even more rare animal life. Rocky outcroppings of greywacke and Franciscan sandstone and coastal prairie grasslands provide habitat for the four threatened or endangered butterflies covered in the HCP, the mission blue, San Bruno elfin, callippe silverspot, and the recently reintroduced bay checkerspot butterfly.
In the springtime, visitors are treated to a magnificent display of wildflowers: lupines, California poppies, Indian paintbrush, purple owl’s clover and many more native wildflowers add color and life to the Mountain.
Stewarding San Bruno Mountain’s rich biodiversity going forward is critical. The loss of grasslands and spread of invasive species threatens the delicate balance of life on the mountain.
Evidence suggests that San Bruno Mountain was first settled by Native Americans, likely Ohlone, more than 5,000 years ago. Middens, or shell mounds, that date back thousands of years, are found in several locations across the Mountain. These hunters and gatherers lived on and around San Bruno Mountain for centuries.
A pivotal point in history came in the 18th century. The Portolá expedition, led by Don Gaspar de Portolá, was the first recorded land entry and exploration of California by Europeans. In 1769, after passing through what is now Santa Cruz County, the Portolá expedition traveled north along the coastline of what is now San Mateo County. They made their way to present-day Pacifica and up the mountains to what we now call Sweeney Ridge, where they first laid eyes upon the Bahia de San Francisco (San Francisco Bay).
A half-century later, in 1821, victory over Spain in the Mexican War of Independence marked the beginning of Mexican rule in California, which lasted only a few decades. A border dispute in Texas lead to the Mexican-American war and the United States took possession of California in 1848.
In 1884, Charles Crocker, one of the builders of the Central Pacific Railroad, acquired almost 4,000 acres of San Bruno Mountain and for a while the land was simply used for grazing. It wasn’t until the middle of the next century that the San Francisco Peninsula began to see exploding growth and aggressive urbanization threaten many iconic landscapes, including San Bruno Mountain.
In the 1950s and 60s, planners proposed cutting off the top of San Bruno Mountain and dumping it in San Francisco Bay. A similar pattern of development was happening around the Bay where shoreline was being paved at an alarming rate to create new neighborhoods, freeways and runways. When these plans for San Bruno Mountain were resurrected by developers, locals were outraged. A conveyer belt system was proposed to transport the fill over the freeway to offshore barges. Brisbane residents and groups like Save the Bay organized and put an end to this ill-fated idea in 1967.
In 1982, the HCP was put in place that respected the mountain’s unique habitats and rare plant and animal species. While the HCP allows for some development on habitat lands, developers must mitigate impacts by funding the preservation and restoration of similar high-value habitat lands.