4.1 mile out and back hike over a lonely rocky ridge above Woodacre.
Distance, category, and difficulty:
This 4.1 mile out and back hike is moderately easy, with a
total elevation change of about 700 feet. Trailhead elevation is about 800
feet. The preserve's highest elevation is 1418 feet. The trail along the
ridge has some steep and rocky hills.
Mixed sun and shade.
Dirt trails and fire roads.
Very pretty in early spring.
Gas, food, and lodging:
Pay phones, gas, stores, and restaurants in Fairfax. No camping.
From US 101 in Marin County exit Sir Francis Drake/San Anselmo. Drive west
on Sir Francis Drake about 9.5 miles, then turn left onto Railroad Avenue
(near Woodacre). Drive about 0.5 mile, then turn right onto Carson Road.
Drive uphill on narrow and winding Carson Road for about 1 mile, where the
road ends at Conifer Way. Make a very sharp left turn onto Conifer Way and
drive slowly up this dirt road about 0.2 mile, to the open space gate at
the end of the road.
Get driving or public transit directions from Transit and Trails:
GPS coordinates* for trailhead:
(* based on Google Earth
data, shown as degrees, minutes, seconds)
Parking for 3 vehicles in a rough dirt area near the gate. If those spaces
are full, drive back down to Carson Road and park on the side of the road
anywhere legal. Local restrictions demand that cars park at least 6 feet
from the center of the road, so look for a pullout all the way off the pavement.
This is absolutely a bare bones trailhead. No maps, no toilets, and no parking
or entrance fees. No designated handicapped parking, and there is no wheelchair
access. There is no direct public transportation to the trailhead, but Golden
Gate Transit's #23 bus runs along San Geronimo Valley Drive, and you can
walk into the preserve on Bates Canyon Trail, which departs from San Geronimo
All trails are multi-use. Dogs are permitted on leash on trails; off leash
under voice command on fire roads. Dog owners must have a leash for each
The Official Story:
MCOSD field office 415-499-6405
map from the MCOSD website.
Open Spaces, by Barry Spitz, has the best map and detailed
trail descriptions (order
this book from Amazon.com).
Hiking Marin, by Don and Kay Martin, has a useful map and
some preserve descriptions, as well as driving directions to other trailheads
at this preserve (order
this book from Amazon.com).
The Bay Area Ridge Trail, by Jean Rusmore (order
this book from Amazon.com), has a decent map and descriptions of the
Ridge Trail segment though the preserve.
View 50 photos from
the featured hike.
Go to Bay Area Hiker Home page
those who love hiking on Tam but experience seasonal weariness due to fair weather crowds and that "been there,
done that," feeling, have I got a preserve for you. Gary Giacomini
Open Space Preserve, which runs along the north side of the San Geronimo
Ridge between Sir Francis Drake and Fairfax-Bolinas Road, will have you
looking at northern Marin County in a whole new way, literally. There's
excitement and drama (driving on tiny winding roads, searching for the
trailheads, gambling on the availability of parking), and a rugged, unsigned
trail system not for sissies. Besides the surprisingly remote feeling
of Giacomini, the main trail, San Geronimo Ridge Fire Road, affords amazing
views of northern and western Marin County, including a clear sight of
Sugarloaf Ridge on a fog-free day. When
the crowds throng to Tam, and you just can't stand to get stuck behind
another slow-moving car full of out-of-towners on
the way up to Ridgecrest, it's nice to have a no-frills, no-tourist preserve
in your repertoire.
The preserve's long ridge-top route is a
favorite for cyclists combing Giacomini's fire roads with MMWD's Pine
Mountain Road. For hikers short loops are pretty much out of the question,
although if you treat the side of San Geronimo Valley Road as a trail
you can combine that street with Conifer Fire Road (via Bates Canyon Trail),
San Geronimo Ridge Fire Road, and Sylvestris Fire Road for a 5 mile trek.
Out and back hikes from three trailheads above San Geronimo Valley Road
and one near the edge of Samuel P. Taylor State Park involve a climb to
the ridge line and then a stroll along San Geronimo Ridge Fire Road. From
the trailhead at the end of Conifer Way hikers can ascend to the
ridge, then walk east out-and-back to the top of White Hill. This is a
nice alternate to the featured hike, or a 3 mile add-on, but it's a bit
of a roller coaster route.
Most of the ridge is under full sun and can get
super hot. Spring and autumn are good seasons for a visit. In spring there
are good flowers on chaparral shrubs and through the grassland. Parts
of San Geronimo Ridge Fire Road are steep and rocky, so even short
hikes can exhaust your feet and lower legs. Sturdy hiking boots,
and plenty of drinking water are a must.
For the featured hike, start at the open
space gate at the end of Conifer Way (or, if you've parked on Carson
Road, walk to the end of Conifer Way). Initially, the trail climbs through
grassland, but at about 350 feet, you'll take a curve to the right near
a water tank and head under the shade of madrone, Douglas fir, and California bay. On the slope of
the hill to the right, some bush poppy and manzanita struggle for sun.
In more shaded stretches hazelnut and monkeyflower are common. Forget-me-nots
bloom in the spring, along with strawberries and iris, and you may even
see a few striking red spotted coralroots, a saprophytic orchid. The grade
shifts from moderate to steep, and the shade is delicious on a hot day.
Conifer Fire Road emerges into grassland, and continues to climb. Views
back to the north are impressive, and they only get better. Spring flowers
along the fire road include blue-eyed grass, California poppy, and fiddlenecks.
Look for a spot off the right side of the trail between two hills, where
in the spring creamcups and California buttercups sprawl through the grass,
and checker-blooms provide a burst of pink color. At 0.80 mile, a connector
path breaks off on the left. Continue to the right on Conifer
More spring flowers can be found along the
trail here, including scarlet pimpernel and redmaids, but creamcups dominate. At 0.91 mile, Conifer Fire Road ends at an unsigned junction with
San Geronimo Fire Road. Turn right onto San Geronimo Ridge Fire Road.
The land on the left side of the trail is
part of the Marin Municipal Water District, while the land to the right
is Marin County Open Space District property. The fire road crosses a
fence line, and abruptly, it's like stepping into another world. Gone
are the treeless grassy slopes, replaced by a rocky, chaparral plant community
and many shrubby sargent cypress trees. The fire road climbs easily, through
manzanita, chamise, chaparral pea, and toyon. Jackrabbits and lizards
are common on the ground, and in the air you may see hawks and vultures.
White and purple iris seem out of place, but flourish in spring along with
paintbrush, mission bells, and zigadene. Where foliage is low, look to
the right of the trail (north), for far-reaching views that include the
tallest hills in northern Marin County, such as Big Rock Ridge and Black
Mountain, and even stretch to Sugarloaf Ridge in Sonoma County. Forested
Mount Wittenberg, on the Point Reyes Peninsula, is evident to the west
on a clear day. Although the little town of San Geronimo is a short distance
downhill, the ridge is very quiet. I wonder how many people, if magically
transported to this part of the preserve, could correctly identify their
location. I always feel like I'm somewhere more remote than Marin County.
After a mostly level stretch, the trail begins a moderate descent. At
a flat spot, San Geronimo Ridge Fire Road comes to an unsigned junction
at 1.88 miles. Pine Mountain Fire Road drops down south to Fairfax-Bolinas
Road on the left. Sylvestris Fire Road departs on the right side of the
trail. (To extend this hike another
mile, take Sylvestris to Hunt Camp, turn left, then when you reach San
Geronimo Ridge Fire Road again, turn left.) Continue straight uphill
on San Geronimo Ridge Fire Road.
You'll pass through a pocket of woods, with
Douglas fir, coast live oak, and madrone. Look for woodland star and shooting
star in spring. San Geronimo Ridge Fire Road climbs steeply. Once out
of the woods buckbrush, blueblossom, and wavyleaf ceanothus, members of
buckthorn family, line the sides of the trail, along with manzanitas,
chaparral pea, toyon, chinquapin, and yerba-santa. At 2.10 miles, you'll
reach a viewpoint. Look downhill for a spectacular view of Kent Lake.
To the south, all three peaks of Mount Tamalpais may be visible. This
is the turn-around point for this hike. (You can continue further on San
Geronimo Ridge Fire Road if you'd like.) Retrace your steps back to
Total distance: 4.10 miles
Last hiked: Thursday, November