San Geronimo Ridge Road via B-17 Trail loop

Parking is available at various access points for the White Hill Open Space Preserve. Specific trailhead parking for the San Geronimo Ridge Road can be found, but it's advisable to check the Marin County Parks website for the most current information on parking regulations and availability.

Yes, dogs are welcome on the trail. However, leash requirements can vary between different trails and fire roads within the preserve, so always be mindful of signage.

The trail offers diverse beauty throughout the year. Spring brings vibrant wildflowers like California poppies and irises, while fall showcases picturesque orange and yellow foliage. The varied micro-climates mean it can be enjoyed in different seasons, but checking current trail conditions is always recommended.

Generally, there are no permits or entrance fees required to access the Gary Giacomini Open Space Preserve or the White Hill Open Space Preserve where this loop is located. However, it's always a good idea to check the Marin County Parks website for any updates or specific regulations.

The loop features a mix of wide fire roads and some singletrack sections. You'll traverse dirt and gravel surfaces, moving through oak woodlands, chaparral-covered hills, and redwood canyons. Expect some rocky areas and grassy meadows, including a unique pygmy Sargent cypress forest.

You'll be treated to extensive panoramic views, including 360-degree vistas of the North Bay, deep canyons, wooded ridges, and Mount Tamalpais. A notable feature is the Pygmy (dwarf) sargent cypress forest, where ancient trees are dwarfed by serpentine soil. You'll also get dramatic views down to scenic Kent Lake.

This loop is rated as difficult due to its length and elevation gain of approximately 700 meters. While there are sustained climbs, they are generally not overly steep, and the fire roads are well-maintained. It requires good fitness and sure-footedness, but options exist for more moderate sections if you don't complete the full loop.

The full loop, covering about 18.3 kilometers with 700 meters of elevation gain, typically takes around 5 to 6 hours to complete, depending on your pace and stops for enjoying the scenery.

Yes, the trail system is extensive and connects to adjacent preserves. Along this route, you'll find sections of the Bay Area Ridge Trail - 01 - North Bay, White Hill Fire Road, Happenberger Ridge Trail - Pine Mountain Fire Rd, San Geronimo Ridge Road, and the B-17 Trail itself, allowing for longer, interconnected hiking possibilities.

While the trail itself has a remote feel, the nearby towns of Fairfax and San Geronimo offer amenities such as cafes, pubs, and accommodation where you can resupply or relax before or after your hike.

Given its length and remote sections, it's wise to carry plenty of water and snacks. The trail offers varied micro-climates, so dressing in layers is recommended. While the fire roads are generally clear, some singletrack sections require attention. The historical site of a B-17 bomber crash from 1946 is also nearby, adding a point of interest.