2. John Muir
One of the most famous naturalists ever and a definitive pioneer in the preservation movement, John Muir co-founded the Sierra Club and wrote several books about his outdoor explorations. Muir originally left his native Scotland to study Yosemite National Park, but later chose to stay in America and proclaim the gospel of the wilderness. Always more at home outdoors than in, Muir became an evangelist for the naturalist movement, and described himself as a disciple of Henry David Thoreau. Muir's belief in the divinity of nature permeates his writings and even influenced Theodore Roosevelt who, while he was US president, once took a four-day camping trip in the Yosemite wilderness with Muir.
Muir is the author of numerous books including "My First Summer in the Sierra" and "A Thousand Mile Walk to the Gulf."