Enos Mills (1870-1922), a self-taught natural historian, had four related careers: mountain guide in Estes Park, Colorado; innkeeper, promoting Colorado tourism; lobbyist and spokesman for national parks; writer of books and articles on the outdoors. Mills found his greatest success as a writer. The author discusses his writings in depth, the influence of John Muir, Mills's activity in creating Rocky Mountain National Park, and his pioneering work with the nature guide concept in the national parks. His writings and career influenced the development of American attitudes toward nature. Based on Mills's writings, secondary sources, contemporary newspapers, and the Enos Mills Papers in the Denver Public Library