John Muir was a Scottish-American naturalist who explored and wrote about the wild mountains and forests of California, especially Yosemite. In 1903 he took President Theodore Roosevelt on a camping trip through Yosemite, just the two of them for part of it, a trip widely credited with inspiring Roosevelt's sweeping expansion of America's protected lands. His writing convinced the U.S. government to protect wild lands as national parks, and he helped found the Sierra Club, an organization still working to protect nature today — earning him the nickname "Father of the National Parks."