It’s about as suburban as San Francisco gets. Among the townhouses and condominiums of Diamond Heights, part of the city’s massive post-war redevelopment land grab, there’s a shopping center with a Safeway, a post office, a dim sum palace, and a drugstore. But it’s also a gateway to one of the few vestiges of an older, wilder San Francisco: Glen Canyon.
Follow a simple dirt path behind the loading docks, around the backside of George Christopher Playground, currently closed for renovations, and past a Little League field. Suddenly, miraculously, the lush, rocky canyon is at your feet.
It’s not the only entrance to Glen Canyon Park, but it’s the most spectacular one. From this vantage, the canyon is deep and steep and rough like a gash. Islais Creek gurgles through the underbrush, a rare uncovered city stream.
Blue gum eucalyptus march down the canyon’s slopes and provide habitat for owls and hawks, who eye the grasslands below for prey among the coyote brush and other coastal scrub. In the spring, the canyon’s meadows bloom with California poppy, blue-eyed grass, checkerbloom, and mule’s ears.
A network of dirt trails reaches all the way to the canyon’s bottom, where a walk is shady and cool. Islais Creek plays hide-and-seek in the undergrowth and at one point is fed from a mini marshland that requires a wooden boardwalk to traverse.
If you follow the creek uphill, the track grows narrower, and the surroundings wilder. Willows arch overhead and songbirds hidden among the branches call to each other. While the park’s hillside trails, meadows, and stands of eucalyptus recall the city’s other green spaces, the creek feels different from the rest of San Francisco simply because it is. Lobos Creek in the Presidio is the only other year-round stream flowing above ground in the city, but much of it is off-limits.
(The canyon also represents the headwaters of a once-unimaginable vision: restoring wetlands and daylighting Islais Creek at its eastern end where it meets the Bay.)
Walkers can also stick to the sun, if there is any that day, and wind up the slopes past rocky outcrops — some of which are authorized for outdoor bouldering in the city. The rocks, called radiolarian chert, contain the remnants of countless ancient marine plankton, uplifted over millennia from the sea floor. (San Francisco’s hills make for geological wonders if you know where to look.)
For the city’s best views and an even better workout — nearly two miles and an elevation gain of 850 feet — hike to the top of Glen Canyon, past the Ruth Asawa School of the Arts, and connect to the trail that climbs to the top of Twin Peaks.
Gum Tree Girls
Because of the varied trails and the well-appointed recreation center, playground, tennis courts, and ball field at the mouth of the canyon, Glen Canyon Park also feels social in a way that many city parks don’t, providing an extended backyard for the cozy Glen Park neighborhood. On a weekday morning, hikers, joggers, and dog walkers say hello to each other as they pass. A group of moms with strollers hangs out by the rec center, and a grandmother chases after a towheaded toddler who is chattering about bees. It’s the sort of place where strangers stop one another to relay news of a wildlife sighting. (During a recent visit, a coyote sunning itself in a meadow stole the show.)
The communal nature of this park shouldn’t surprise, as it exists in its current form thanks to neighborhood activism. In the 1960s, the city wanted to make O’Shaughnessy Boulevard, which snakes along the canyon’s western flank, an extension of the nearby I-280 freeway. A group of Glen Park mothers banded together to fight the proposal. They were nicknamed the “Gum Tree Girls” by those who dismissed their efforts.
But the women persevered, taking up their cause at PTA meetings, churches, and neighborhood groups. They even took a lunch that included “a thermos of martinis” to then-Supervisor George Moscone’s office, the Glen Park News reported. In 1967, the city shelved the plan, and Glen Canyon Park was saved.
Hidden history
Before Europeans arrived, the canyon was hunting grounds for the local Yelamu tribe, part of the Ohlone/Costanoan people. Spanish missionaries used the land as pasture for sheep and cattle. When the United States annexed California from Mexico in 1848, the canyon was part of Rancho San Miguel, one of many sprawling land grants across the state.
Soon after statehood, Glen Canyon Park made history. (It is, in fact, California Historical Landmark number 1,002.) In 1868, the first commercial dynamite manufacturer in the U.S., Giant Powder Company, won an exclusive license from inventor Alfred Nobel and set up shop in the canyon because of its distance from populated areas. Good thing, too: the factory was completely destroyed in an explosion in late 1869. It left two dead and nine others injured, and the factory — whose precise location is unknown but was likely near the present-day rec center — was never rebuilt in Glen Canyon.
[Correction: A previous version of this story stated there was no plaque to commemorate the canyon’s dynamite factory. A plaque was in fact dedicated in 2018.]
In the late 1880s, the Crocker Real Estate Company purchased the land from Adolph Sutro, who at one point owned one-twelfth of the city’s acreage. The company transformed it into the Glen Park Picnic Grounds, with a small zoo, an aviary, a bowling alley, and hot air balloon rides. Jimmy “Scarface” Williams walked a tightrope suspended over the canyon to delight and frighten picnickers.
A creek runs through it
In 1922, after Glen Park residents began to complain that the picnic grounds were spawning too many drunken brawls, the city purchased the land from Crocker for $30,000. The rec center, which includes a gymnasium and auditorium, was built in 1937 by the Works Progress Administration, with a day camp added in the 1950s. (The camp is still there, a short walk up from the rec center, hosting summer camps for city kids and a preschool during the school year.)
But one of the most significant changes to Glen Canyon came in 1941 with the completion of O’Shaughnessy Boulevard. The four-lane road cut off the western side of the watershed that feeds Islais Creek, which reportedly once held enough water to float a boat in certain sections. In some places today, the only sign of its existence is the water-loving plants that thrive: willows, horsetail, seep monkey flower, and red columbine. Several days after late November’s strong rains, the creek was, at best, a trickle before it headed underground just above the rec center. It stays buried for three miles before reemerging into daylight north of the Bayview’s Heron’s Head Park.
Even as a slender stream, Islais Creek provides essential riparian habitat for a whole food web of animals, from insects to amphibians and reptiles to resident and migratory birds. The creek not only serves as a buffet for these avian visitors, but it also provides crucial shelter and fresh water. Lisa Wayne, the natural resource manager for San Francisco Recreation and Parks, likens the creek to Glen Canyon’s “spinal cord.”
“We’ve seen a lot of loss, honestly, in terms of the kinds of species, butterflies, animals, and plants throughout our city over the course of time, obviously, due to a lot of urban development and other pressures,” Wayne says.
With the canyon designated a Significant Natural Resource Area, the focus is removing invasive plants, like cape ivy; protecting habitat for native species, such as rare lilies and onions that compete for space with annual grasses; and restoring trails in an ecologically sensitive way. An attempt last decade to reintroduce the endangered San Francisco forktail damselfly unfortunately didn’t take; there has not been an attempt since, according to Wayne.
“If you only have three plants and then someone comes along and picks a plant, or it doesn’t reproduce that year, they can quickly blink out,” Wayne says.
Volunteers organized through Rec and Parks and Friends of Glen Canyon Park do much of the work.
After you’ve explored the canyon’s trails, climbed its rocks, and perhaps spotted a coyote, a reward is easy. Head a few blocks east to Glen Park’s commercial cluster for a wide range of treats. We’re partial to the old-school cocktails at Glen Park Station, the deli counter at Cheese Boutique, and the books and live jazz at Bird & Beckett.
How to get there
Glen Canyon Park has several entrances. While the most stunning one is located by George Christopher Playground behind the Diamond Heights shopping center, the most accessible entrances are off Bosworth Avenue (right where it turns into O’Shaughnessy Boulevard) and on Elk Street at Chenery Street by the Glen Park Recreation Center. Both are a short walk from the Glen Park BART station, and the 44 and 52 Muni lines encircle the canyon. Neighborhood parking is easy to find (except, perhaps, on busier weekends). Many of the trails are steep and unpaved, which could be difficult for people with limited mobility.
