John Muir was born on April 21^th, 1838, the third of eight children in Dunbar, East Lothian, Scotland.

His strict upbringing centred on religion brought out his rebellious side and his love of nature. At a young age he was a "restless spirit" and especially "prone to lashings." He never came to terms with his Fathers views that anything other than Bible studies was “frivolous and punishable”. 

In 1849 his Father decided the Church of Scotland was too lenient and the family emigrated to the United States to Fountain Lake Farm, near Portage, Wisconsin. The new congregation they joined was called the Disciples of Christ. The influence on the young Muir, aged 11 meant he learned to recite "by heart and by sore flesh" all of the New Testament and most of the Old Testament. 

When he was 22 years old, John Muir enrolled at the University of Wisconsin–Madison, paying his own way for several years. In his first year Muir studied chemistry with Professor Ezra Carr and his wife Jeanne. He continued studying a variety of science courses and despite never graduating learned plenty about geology and botany.   

In 1863 with the military draft looming, his brother Daniel left for Canada to avoid the draft and convinced John to do the same. Spending a year exploring lakes and swamps around Lake Huron collecting plants Muir soon ran low on money and reunited with his brother in Ontario where the two worked on a sawmill for a year. 

Muir soon returned to the United States, settling in Indianapolis using his newfound woodwork skills as a sawyer in a wagon wheel factory. His inventive mind proved valuable to his employers, he was constantly finding new ways to improve productivity of the machinery and processes. However in early March 1867 an accident changed the course of his life; he was struck in the eye after he slipped using a sharp tool work. Muir was confined to a darkened room for six weeks, not knowing if he would ever regain his sight. He did. He later wrote in his autobiography "This affliction has driven me to the sweet fields. God has to nearly kill us sometimes, to teach us lessons". From that point on, he determined to "be true to himself" and follow his dream of exploration and study of plants.

With his newfound outlook on life, in September 1867 Muir went on a 1000 mile walk from Indiana to Florida. Without a planned route he vowed to go by the "wildest, leafiest, and least trodden way I could find" 

Arriving at Cedar Keys, he began work at a sawmill but after three days contracted severe malaria.

After recovering he decided to go to Cuba via the ‘Island Belle.  In Havana, he studied shells and flowers before returning to New York. Once there he booked a passage to California. 

Settling in San Francisco, the restless Muir immediately left for a week-long visit to Yosemite, a place he had only read about. Muir notes that "He was overwhelmed by the landscape, scrambling down steep cliff faces to get a closer look at the waterfalls, whooping and howling at the vistas, jumping tirelessly from flower to flower." 

He built a small cabin along Yosemite Creek, designing it so that a stream flowed through a corner of the room so he could enjoy the sound of running water. He lived in the cabin for two years. 

During his first summer in the Sierra he worked as a shepherd, Muir wrote field notes that emphasized the role that the senses play in human perceptions of the environment. He speculated that the world was an unchanging entity that was interpreted by the brain through the senses, and, writes Muir, "If the creator were to bestow a new set of senses upon us . . . we would never doubt that we were in another world. . . " While doing his studies of nature, he would try to remember everything he observed as if his senses were recording the impressions. As a result of his intense desire to remember facts, he filled his field journals with notes on precipitation, temperature, and even cloud formations. 

During these years in Yosemite, Muir was unmarried, often unemployed, with no prospects for a career. He was sustained by the natural environment, and by reading the essays of naturalist author Ralph Waldo Emerson, who wrote about the very life that Muir was then living. On excursions into the back country of Yosemite, he traveled alone, carrying "only a tin cup, a handful of tea, a loaf of bread, and a copy of Emerson.  His evenings were spent sitting by a campfire in his overcoat, reading Emerson under the stars. As the years passed, he became a "fixture in the valley," respected for his knowledge of natural history, his skill as a guide, and his vivid storytelling. 

By 1871, Muir had lived in Yosemite for three years, Emerson, with a number of academic friends from Boston, arrived in Yosemite during a tour of the Western United States. The two men met, and according to Tallmadge, "Emerson was delighted to find at the end of his career the prophet-naturalist he had called for so long ago. . . And for Muir, Emerson's visit came like a laying on of hands." Emerson spent only the one day with Muir, although he offered him a teaching position at Harvard, which Muir declined. Muir later wrote, "I never for a moment thought of giving up God's big show for a mere profship!" 

Pursuit of his love of science, especially geology, often occupied his free time. Muir soon became convinced that glaciers had sculpted many of the features of the Yosemite Valley and surrounding area. This notion was in stark contradiction to the accepted contemporary theory, which attributed the formation of the valley to a catastrophic earthquake. As Muir's ideas spread, Josiah Whitney (head of the California Geological Survey, tried to discredit Muir by branding him as an amateur. But Louis Agassiz, the premier geologist of the day, saw merit in Muir's ideas, and lauded him as "the first man I have ever found who has any adequate conception of glacial action." 

Muir was a highly productive writer and had many of his accounts and papers published as far away as New York. Muir's former professor at the University of Wisconsin, Ezra Carr, and his wife Jeanne, encouraged Muir to put his ideas into print. 

A large earthquake centered near Lone Pine, California, in Owens Valley strongly shook occupants of Yosemite Valley in March 1872. The quake woke Muir in the early morning and he ran out of his cabin "both glad and frightened," exclaiming, "A noble earthquake!" Other valley settlers, who believed Whitney's ideas, feared that the quake was a prelude to a cataclysmic deepening of the valley. Muir had no such fear and promptly made a moonlit survey of new talus piles created by earthquake-triggered rockslides. 

In addition to his geologic studies, Muir also investigated the plant life of the Yosemite area. In 1873 and 1874, he made field studies along the western flank of the Sierra on the distribution and ecology of isolated groves of Giant Sequoia. In 1876, the American Association for the Advancement of Science published Muir's paper on the subject. 

In 1878, when he was nearing the age of 40, Muir’s friends "pressured him to return to society." Soon after he returned to the Oakland area, he was introduced by his great friend Jeanne Carr to Louisa Strentzel, daughter of a prominent physician and horticulturist with a 2,600-acre fruit orchard in Martinez, California, northeast of Oakland. In 1880, after he returned from a trip to Alaska, Muir and Strentzel married. John Muir went into partnership with his father-in-law, Dr. John Strentzel, and for many years directed most of his energy into managing this large fruit ranch. Although Muir was a loyal, dedicated husband, and father of two daughters, "his heart remained wild," writes Marquis. His wife understood his needs, and after seeing his restlessness at the ranch would sometimes "shoo him back up" to the mountains. 

Muir first travelled to Alaska in 1879 and was the first Euro-American to explore Glacier Bay. He travelled into British Columbia a third of the way up the Stikine River, likening its Grand Canyon to "a Yosemite that was a hundred miles long" and recorded over 300 glaciers along the river's course.

He returned for further explorations in Southeast Alaska in 1880, and in 1881 was with the party that landed on Wrangel Island on the USS Corwin and claimed that island for the United States. In 1888 after seven years of managing the ranch, his health began to suffer. He returned to the hills to recover, climbing Mt. Rainier in Washington and writing Ascent of Mount Rainier. 

Muir threw himself into the preservationist role with great vigor seeing the Yosemite area and the Sierra as pristine lands. He thought the greatest threat to the area was domesticated livestock—especially sheep, which he referred to as "hoofed locusts". 

In June 1889, the influential associate editor of Century magazine, Robert Underwood Johnson, camped with Muir in Tuolumne Meadows and saw firsthand the damage a large flock of sheep had done to the grassland. Johnson agreed to publish any article Muir wrote on the subject of excluding livestock from the Sierra high country. He also agreed to use his influence to introduce a bill to Congress to make the Yosemite area into a national park. 

On September 30, 1890, the U.S. Congress passed a bill that essentially followed recommendations that Muir had suggested in two Century articles, The Treasure of the Yosemite and Features of the Proposed National Park, both published in 1890. But to Muir's dismay, the bill left Yosemite Valley under state control, as it had been since the 1860s. 

In early 1892, Professor Henry Senger, a philologist at the University of California, Berkeley, contacted Muir with the idea of forming a local 'alpine club' for mountain lovers. Senger and San Francisco attorney Warren Olney sent out invitations "for the purpose of forming a 'Sierra Club.' Mr. John Muir will preside." On May 28, 1892, the first meeting of the Sierra Club was held to write articles of incorporation. One week later Muir was elected president. He remained so until his death 22 years later. 

The Sierra Club immediately opposed efforts to reduce Yosemite National Park by half, and began holding educational and scientific meetings.  It was active in the eventual successful campaign to transfer Yosemite National Park from state to federal control in 1906. The fight to preserve Hetch Hetchy Valley was also taken up by the Sierra Club, with some prominent San Francisco members opposing the fight. Eventually a vote was held that overwhelmingly put the Sierra Club behind the opposition to Hetch Hetchy Dam. 

In July 1896, Muir became associated with Gifford Pinchot, a national leader in the conservation movement. Pinchot was the first head of the United States Forest Service and a leading spokesman for the sustainable use of natural resources for the benefit of the people. His views eventually clashed with Muir's and highlighted two diverging views of the use of the country's natural resources. Pinchot saw conservation as a means of managing the nation's natural resources for long-term sustainable commercial use. As a professional forester, his view was that "forestry is tree farming," without destroying the long-term viability of the forests. Muir valued nature for its spiritual and transcendental qualities. In one essay about the National Parks, he referred to them as "places for rest, inspiration, and prayers." 

Their friendship ended in the summer of 1897 when Pinchot released a statement to a newspaper supporting sheep grazing in forest reserves. Muir confronted Pinchot and demanded an explanation. When Pinchot reiterated his position, Muir told him: "I don't want any thing more to do with you." This philosophical divide soon expanded and split the conservation movement into two camps: the preservationists, led by Muir; and Pinchot's camp, who co-opted the term "conservation." Their contrasting views were highlighted again when the United States was deciding whether to dam Hetch Hetchy Valley. Pinchot favored damming the valley as "the highest possible use which could be made of it." In contrast, Muir proclaimed, "Dam Hetch Hetchy! As well dam for water-tanks the people's cathedrals and churches, for no holier temple has ever been consecrated by the hearts of man." 

In 1899, Muir accompanied railroad executive E. H. Harriman and esteemed scientists on the famous exploratory voyage along the Alaska coast aboard the luxuriously refitted 250-foot steamer, the George W. Elder. He later relied on this friendship to pressure Congress to pass conservation legislation. 

In 1903, President Theodore Roosevelt accompanied Muir on a visit to Yosemite. Muir joined Roosevelt in Oakland, California, for the train trip to Raymond. The presidential entourage then traveled by stagecoach into the park. During this journey Muir told the president about state mismanagement of the valley and rampant exploitation of the valley's resources. Even before they entered the park, he was able to convince Roosevelt that the best way to protect the valley was through federal control and management. 

Upon entering the park and seeing the magnificent splendor of the valley, the president asked Muir to show him the real Yosemite. Muir and Roosevelt set off largely by themselves and camped in the back country. The duo talked late into the night, slept in the brisk open air of Glacier Point, and were dusted by a fresh snowfall in the morning. It was a night Roosevelt never forgot. 

Muir's attitude toward Native Americans evolved over his life. His earliest encounters were with the Winnebago Indians in Wisconsin, who begged for food and stole his favorite horse. He had a great deal of sympathy for their "being robbed of their lands and pushed ruthlessly back into narrower and narrower limits by alien races who were cutting off their means of livelihood." His early encounters with the Paiute in California left him feeling ambivalent after seeing their lifestyle, which he described as "lazy" and "superstitious". Later, after living with Indians, he praised and grew more respectful of their low impact on the wilderness, compared to the heavy impact by European-Americans. 

With population growth continuing in San Francisco, political pressure increased to dam the Tuolumne River for use as a water reservoir. Muir passionately opposed the damming of Hetch Hetchy Valley because he found it as stunning as Yosemite Valley. Muir, the Sierra Club and Robert Underwood Johnson fought against inundating the valley. Muir wrote to President Roosevelt pleading for him to scuttle the project. Roosevelt's successor, William Howard Taft, suspended the Interior Department's approval for the Hetch Hetchy right-of-way. After years of national debate, Taft's successor Woodrow Wilson signed the bill authorizing the dam into law on December 19, 1913. Muir felt a great loss from the destruction of the valley, his last major battle. 

In his life, Muir published six volumes of writings, all describing explorations of natural settings. His first appearance in print was by accident, when a person he did not know submitted, without his permission or awareness, a personal letter to his friend Jeanne Carr, describing Calypso borealis, a rare flower he had encountered. The piece was published anonymously, identified as having been written by an "inspired pilgrim". Throughout his many years as a nature writer, Muir frequently rewrote and expanded on earlier writings from his journals, as well as articles published in magazines. He often compiled and organized such earlier writings as collections of essays or included them as part of narrative books. 

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 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 also recycled his earlier writings partly due to his "dislike of the writing process and 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." 

He understood that to discover truth, he must turn to what he believed were the most accurate sources. In his book, The Story of My Boyhood and Youth (1913), he writes that during his childhood, his father made him read the Bible every day. Muir eventually memorized three quarters of the Old Testament and all of the New Testament. Muir's father read Josephus's War of the Jews to understand the culture of first-century Palestine, as it was written by an eyewitness, and illuminated the culture during the period of the New Testament. But as Muir became attached to the American natural landscapes he explored, Williams notes that he began to see another "primary source for understanding God: the Book of Nature." According to Williams, in nature, especially in the wilderness, Muir was able to study the plants and animals in an environment that he believed "came straight from the hand of God, uncorrupted by civilization and domestication." Muir's belief in this "Book of Nature" compelled him to tell the story of "this creation in words any reader could understand." As a result, his writings were to become "prophecy, for they sought to change our angle of vision." 

Muir's philosophy and world view rotated around his perceived dichotomy between civilization and nature. From this developed his core belief that "wild is superior". His nature writings became a "synthesis of natural theology" with scripture that helped him understand the origins of the natural world. According to Williams, philosophers and theologians such as Thomas Dick suggested that the "best place to discover the true attributes of deity was in Nature." He came to believe that God was always active in the creation of life and thereby kept the natural order of the world. As a result, Muir "styled himself as a John the Baptist," adds Williams, "whose duty was to immerse in 'mountain baptism' everyone he could." Williams concludes that Muir saw nature as a great teacher, "revealing the mind of God," and this belief became the central theme of his later journeys and the "subtext" of his nature writing. 

However, Muir took his journal entries further than recording factual observations. Williams notes that the observations he recorded amounted to a description of "the sublimity of Nature," and what amounted to "an aesthetic and spiritual notebook." Muir felt that his task was more than just recording "phenomena," but also to "illuminate the spiritual implications of those phenomena." Muir, mountain skies, seemed painted with light, and came to "...symbolize divinity." 

Muir often used the term "home" as a metaphor for both nature and his general attitude toward the "natural world itself," notes Holmes. He often used domestic language to describe his scientific observations, as when he saw nature as providing a home for even the smallest plant life: "the little purple plant, tended by its Maker, closed its petals, crouched low in its crevice of a home, and enjoyed the storm in safety." Muir also saw nature as his own home, as when he wrote friends and described the Sierra as "God's mountain mansion." He considered not only the mountains as home, however, as he also felt a closeness even to the smallest objects: "The very stones seem talkative, sympathetic, brotherly. No wonder when we consider that we all have the same Father and Mother." 

Not surprisingly, Muir's deep-seated feeling about nature as being his true home led to tension with his family at his home in Martinez, California. He once told a visitor to his ranch there, "This is a good place to be housed in during stormy weather, . . . to write in, and to raise children in, but it is not my home. Up there," pointing towards the Sierra Nevada, "is my home." 

John Muir died at California Hospital in Los Angeles on December 24, 1914 of pneumonia at age 76, after a brief visit to Daggett, California.