From San Francisco Online:

"Muir Woods is located just 17 miles northwest of San Francisco just off Highway 1. The park was named after naturalist John Muir who was instrumental in establishing the National Park system. This National Monument is made up of over 560 acres of redwood forest. Cathedral and Bohemian Groves contain the largest Coast redwoodsÜp;up to 252 feet tall and 14 feet across. Today the Sequoia sempervirens can be found only in the damp and cool coastal belt that runs from Monterey to Oregon. Visitors are invited to explore the paved main trail which offers educational exhibits on the majestic redwood treesÜp; some known to be 1,000 years old. There are six miles of walking trails and no cars are allowed in the redwood grove."