From US 101 in Marin County, exit #463 (San Marin Drive/Atherton Avenue). Drive west on San Marin Drive about 3 miles, then turn right onto Novato Boulevard. Drive about 2.5 miles on Novato Boulevard, then turn left into the park. Once past the entrance kiosk, turn right and continue to the end of the paved parking area, about 0.4 mile from the entrance. $5 single vehicle entrance fee ($2 to walk in); pay at the automated machine at the entrance if kiosk is unattended. Read more details here.