The Marin County Open Space District, which turns 40 this year, was born from a heroic movement to preserve natural lands and contain urban sprawl. Today it administers 34 preserves—all but one of them dog-friendly—totaling more than 20,000 acres and providing Bay Area residents and visitors with many ways to play. Four-legged hikers enjoy the rare privilege of accompanying their humans off-leash on the fire roads in the preserves, and while tethers are required on other trails, none of the paths are off limits to canines.
While each preserve has its own features and flavor, two of the more lightly visited tracts are among our DogTrekker favorites. Indian Tree Preserve near Novato is notable for the shaded trails that offer respite on hot summer days. Plan about 3.5 hours for a 5.5-mile loop hike on the Upper Meadow and Big Trees trails, the latter of which traces a zig-zag pattern as it climbs a stiff 1,200 feet to a wide-open summit with forever views.
At Gary Giacomini Open Space Preserve, the higher you climb, the grassier it gets. You'll see few other hikers even on the fire road that runs along lonely San Geronimo Ridge (although you may encounter some cyclists). This four-mile out-and-back hike is relatively easy except when the sun is beating down, so do yourself and your pup a favor and save it for a cloudy day.