Maurice Thorner Memorial Preserve

• Rainy season turns the grasslands lush and green.
• A single, gently sloping trail carries visitors to a low ridge above San Geronimo Valley. Enjoy views of White Hill and Gary Giacomini Preserve on a clear day.
• Thorner Ridge Trail connects to a bridge that crosses Nicasio Valley Road, providing access to Roy's Redwoods Preserve.
• For a longer loop hike take Thorner Ridge Trail to French Ranch Preserve, via a brief walk on Lagunitas School Road.
• The 33-acre preserve was donated by Daniel "Jeff" Thorner, a vice-principal at Terra Linda and San Rafael high schools and a successful businessman.
• Dogs are welcome, but must be leashed at all times.

• See madrone, coyote brush, coast live oak, big-leaf maple, California bay, California nutmeg, and hazelnut trees.
• Spring wildflowers include mariposa lily, and clarkia.
• Listen for the chatter of woodpeckers.
• Check out the iNaturalist field guide. Add your own observations.

• Stay on roads and trails to preserve sensitive ecosystems and to avoid trespassing on private property.
• Dress appropriately for the weather. Trails can be muddy during rainy season. In summer use sun protection–there is no shade.
• Bring water.
• There are no restrooms at this location.
• Steer clear of poison oak.
• After an outing, check for ticks.

From Hwy 101 in Larkspur, take the exit for Sir Francis Drake Blvd west past Fairfax and turn right at Lagunitas School Rd in San Geronimo. MCOSD gate is on the left near the school parking lot.

Street parking only. Please be respectful of local residents. Do not block streets, gates, or driveways.

• Golden Gate Highway and Transportation District
• Marin Transit Trip Planner
• Route from San Rafael Transit Center

You can also dial 511 to find out about transit options from your location.

• Hikers only. No bikes or horses
• No smoking or fires.
• Weapons and hunting prohibited.
• Motorized vehicles prohibited. (Individuals with qualified disabilities may operate certain kinds of zero-emission mobility devices on some roads, multiuse trails, and certain other facilities.)
• No model airplanes, drones, or other self-propelled crafts.
• Dispose of waste property. Pack it out.
• Permit required for commercial use and groups of more than 15 people.
• All resources are protected.

DOGS

• Must be leashed at all times.
• Leash must not exceed 6-feet in length.
• Allowed on signed trails only. Off-trail use prohibited.
• Individuals accompanying dogs are required to clean up and remove pet waste.
• A maximum of 3 dogs per person allowed. No commercial dog walking permitted in this preserve.

In an emergency, call 911. To report an incident or suspicious activity, call the Ranger Field Office at (415) 473-2816 or submit an Incident Report via online form.

Visitors are responsible for knowing and obeying all Marin County Open Space District (MCOSD) regulations. Citations will be issued for violations. Read the official regulations: Marin County Municipal Code Appendix A.

Call (415) 473-6387 for more information regarding allowable types and use of mobility devices for people with qualified disabilities.

The MCOSD is a special district pursuant to the California Public Resources Code. Marin County Parks oversees the management of the county parks system and provides public information on behalf of the MCOSD.