John Muir was a conservationist and environmentalist who is best known for his work in the preservation of wilderness areas in the United States. He was an influential figure in the establishment of the National Park System, and his advocacy for the protection of nature has been credited with inspiring the modern environmental movement. Muir was also a prolific writer, and his writings have been widely read and appreciated by generations of readers. His most famous work, 'My First Summer in the Sierra, ' is considered a classic of American literature.