John Muir also known as "John of the Mountains", was a Scottish-American naturalist, author, environmental philosopher and early advocate of preservation of wilderness in the United States. Today he is referred to as the "Father of the National Parks"

His activism helped to preserve the Yosemite Valley, Sequoia National Park and other wilderness areas.

His letters, essays, and books telling of his adventures in nature, especially in the Sierra Nevada of California, have been read by millions.

The Sierra Club, which he founded, is a prominent American conservation organization.   

The 211-mile (340 km) John Muir Trail, a hiking trail in the Sierra Nevada, was named in his honor. Other such places include Muir Woods National Monument, Muir Beach, John Muir College, Mount Muir, Camp Muir and Muir Glacier. In Scotland, the John Muir Way, a 130 mile long distance route, was named in honor of him.

In his later life, Muir devoted most of his time to the preservation of the Western forests. He petitioned the U.S. Congress for the National Park bill that was passed in 1890, establishing Yosemite National Park. The spiritual quality and enthusiasm toward nature expressed in his writings inspired readers, including presidents and congressmen, to take action to help preserve large nature areas. He is today referred to as the "Father of the National Parks" and the National Park Service has produced a short documentary about his life.

 Muir was noted for being an ecological thinker, political spokesman, and religious prophet, whose writings became a personal guide into nature for countless individuals, making his name "almost ubiquitous" in the modern environmental consciousness.

 Muir published six volumes of writings, all describing explorations of natural settings. Four additional books were published posthumously. Several books were subsequently published that collected essays and articles from various sources.

 Muir's friend, zoologist Henry Fairfield Osborn, writes that Muir's style of writing did not come to him easily, but only with intense effort. "Daily he rose at 4:30 o'clock, and after a simple cup of coffee labored incessantly . . . . he groans over his labors, he writes and rewrites and interpolates." Osborn notes that he preferred using the simplest English language, and therefore admired above all the writings of Carlyle, Emerson and Thoreau. "He is a very firm believer in Thoreau and starts by reading deeply of this author." His secretary, Marion Randall Parsons, also noted that "composition was always slow and laborious for him. . . . Each sentence, each phrase, each word, underwent his critical scrutiny, not once but twenty times before he was satisfied to let it stand."

 Muir often told her, "This business of writing books is a long, tiresome, endless job."

 Muir recycled his earlier writings partly due to his "dislike of the writing process." He adds that Muir "did not enjoy the work, finding it difficult and tedious." He was generally unsatisfied with the finished result, finding prose "a weak instrument for the reality he wished to convey. "However, he was prodded by friends and his wife to keep writing and as a result of their influence he kept at it, although never satisfied.

 Muir wrote in 1872,

 "No amount of word-making will ever make a single soul to 'know' these mountains. One day's exposure to mountains is better than a cartload of books."  In one of his essays, he gave an example of the deficiencies of writing versus experiencing nature.