Muir Woods National Monument is a unit of the National Park Service on Mount Tamalpais near the Pacific coast, in southwestern Marin County, California. It is part of the Golden Gate National Recreation Area, and is 12 miles (19 km) north of San Francisco. It protects 554 acres (224 ha), of which 240 acres (97 ha) are old growth coast redwood (Sequoia sempervirens) forests, one of a few such stands remaining in the San Francisco Bay Area.
One hundred and fifty million years ago ancestors of redwood and sequoia trees grew throughout the United States. Today, the Sequoia sempervirens can be found only in a narrow, cool coastal belt from Monterey, California, in the south to Oregon in the north. Before the logging industry came to California, there were an estimated 2 million acres (8,000 km2) of old growth forest containing redwoods growing in a narrow strip along the coast. By the early 20th century, most of these forests had been cut down. Just north of the San Francisco Bay, one valley named Redwood Canyon remained uncut, mainly due to its relative inaccessibility.
On January 9, 1908, President Theodore Roosevelt declared the land a National Monument, the first to be created from land donated by a private individual. The original suggested name of the monument was the Kent Monument but Kent insisted the monument be named after naturalist John Muir, whose environmental campaigns helped to establish the National Park system.