Simply put, The Muir Woods National Monument is one of the only surviving old-growth coastal redwood forests in the world.
DESCRIPTION FROM DYLANS SITE HERE
One hundred 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 County, California, in the south to Oregon in the north.
Before the logging industry came to California, there were an estimated 2 million acres 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.
This was noticed by William Kent, a rising California politician who would soon be elected to the U.S. Congress. He and his wife, Elizabeth Thacher Kent, purchased 611 acres of land from the Tamalpais Land and Water Company for $45,000 with the goal of protecting the redwoods and the mountain above them.
In 1907, a water company in nearby Sausalito planned to dam Redwood Creek, thereby flooding the valley. When Kent objected to the plan, the water company threatened to use eminent domain and took him to court to attempt to force the project to move ahead. Kent sidestepped the water company's plot by donating 295 acres of the redwood forest to the federal government, thus bypassing the local courts.
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.