John Muir (1838-1914) was a Scottish-born American naturalist, author, and early advocate of preservation of U.S. wilderness. His letters, essays, and books telling of his adventures in nature, especially in the Sierra Nevada mountain range of California, have been read by millions and are still popular today. His direct activism helped to save the Yosemite Valley, Sequoia National Park and other wilderness areas. The Sierra Club, which he founded, is now one of the most important conservation organizations in the United States. His writings and philosophy strongly influenced the formation of the modern environmental movement.