From US 101 in Marin County, exit Sir Francis Drake/San Anselmo. Drive west on Sir Francis Drake about 20 miles, to the junction with CA 1, turn right, drive 0.1 mile, and then turn left onto Bear Valley Road. After about 2 miles, Bear Valley Road ends at Sir Francis Drake; turn left. Continue on Sir Francis Drake about 7.5 more miles, and turn left at the sign "Estero Trail." Drive slowly (there may be cows on this narrow road) about 1 more mile to the trailhead on the right side of the road.