Until the 1800's, many northern California coastal valleys were covered with coast redwood trees similar to those now found in Muir Woods National Monument. The forest along Redwood Creek in today's Muir Woods was spared from logging because it was hard to get to. Noting that Redwood Creek contained one of the San Francisco Bay Area's last uncut stands of old-growth redwood, Congressman William Kent and his wife, Elizabeth Thacher Kent, bought 295 acres here for $45,000 in 1905. To protect the redwoods the Kents donated the land to the United States Federal Government and, in 1908, President Theodore Roosevelt declared it a national monument. Roosevelt suggested naming the area after Kent, but Kent wanted it named for conservationist John Muir.
The above came from http://www.nps.gov/muwo/
Sure are some big trees!