Life and work
David Henry Thoreau was born in Concord, Massachusetts, to John and Cynthia Thoreau. He was named after a recently deceased paternal Uncle, David Thoreau. He didn't change his name to "Henry David" until he had graduated from Harvard, although he never petitioned the government to do so officially. He had two older siblings, Helen and John Jr., and a younger sister, Sophia.

Bronson Alcott notes in his journal that Thoreau pronounced his family name THOR-eau, stress on the first syllable, not the last, a common error today. A Concord variant is THUR-eau, like the English word "thorough." In appearance he was homely, with a nose that he called "my most prominent feature".[Cape Cod] Of his face, Nathaniel Hawthorne wrote: "[Thoreau] is as ugly as sin, long-nosed, queer-mouthed, and with uncouth and rustic, though courteous manners, corresponding very well with such an exterior. But his ugliness is of an honest and agreeable fashion, and becomes him much better than beauty."

Thoreau studied at Harvard between 1833 and 1837, majoring in English. Today, an equivalent degree would be in comparative literature. Legends state that Thoreau refused to pay a five-dollar fee for a Harvard diploma. In fact, the Masters' degree he declined to purchase had no academic merit: Harvard College offered it to graduates "who proved their physical worth by being alive three years after graduating, and their saving, earning, or inheriting quality or condition by having Five Dollars to give the college." (Thoreau's Diploma) His comment was Let every sheep keep its own skin.

Upon graduation, he returned home, where he became a companion of Ralph Waldo Emerson. Emerson took a strong paternal, and sometimes patronizing liking to Thoreau, and delighted advising the young man and introducing him into his social circle, which consisted of some of the most important American writers and thinkers of the period including Ellery Channing, Margaret Fuller, Bronson Alcott, and Nathaniel Hawthorne and his son Julian (at that time only a boy). Of the many esteemed authors who made their home at Concord, he was the only town native. Emerson referred to him as THE man of Concord.

Emerson constantly pushed Thoreau to contribute essays and poems to the transcendentalist magazine, The Dial, but editor Margaret Fuller consented to publish Thoreau's work only after pressure from Emerson. His first work to garner any praise was Natural History of Massachusetts half book review, half natural history essay published in The Dial in 1842.

Like most of his works, the essay was mostly made up of observations Thoreau had made in his journal. Thoreau had begun keeping a journal in 1837 at Emerson's suggestion. His first entry on October 22, 1837 reads, "'What are you doing now?' he [Emerson] asked. 'Do you keep a journal?' So I make my first entry today."

Thoreau was a philosopher of nature and its relation to the human condition. In his early years, he accepted the ideas of Transcendentalism, an eclectic idealist philosophy advocated by Ralph Waldo Emerson, Margaret Fuller, and Bronson Alcott. Transcendentalism was naturalistic and mystical, rejecting deterministic Calvinism. It was inspired by Swedenborg, Kant, Buddhism, Hinduism, and other non-Christian sources. It was not atheistic, but Unitarian and thus did not see Jesus as divine.

Thoreau worked in his father's pencil workshop in 1837-1838. He and his brother John, opened a Grammar School in Concord in 1838, teaching there until John became fatally ill in 1841. In 1841 he was invited to live in the Emerson household, where he lived sporadically until 1843 working as an all-around handyman, gardener, and assistant to Emerson. He spent a few months of 1843 in New York, serving as a tutor to William Emerson's sons, and attempting to break into the New York publishing industry.

The Walden Years: 1845-1847
Thoreau embarked on a two-year experiment in simple living on July 4, 1845 when he moved to a second-growth forest around the shores of beautiful Walden Pond and lived in a tiny self-built house on land owned by Emerson. The house was not in wilderness but at the edge of town, 1.5 miles (2.4 km) from his family home. On a trip into town, he ran into the local tax collector who asked him to pay six years of delinquent poll taxes (1846). Thoreau refused because of his opposition to the Mexican-American War and slavery, for which he spent a night in jail. His later essay on this experience, On the Duty of Civil Disobedience, influenced Leo Tolstoy, Mohandas Gandhi, and Martin Luther King, Jr.

At Walden Pond he completed a first draft of A Week on the Concord and Merrimack Rivers, an elegy to his brother John Thoreau Jr, who had died in 1842 of lock-jaw, describing their 1839 trip to the White Mountains. When the book failed to find a publisher, Emerson urged Thoreau to publish at his own expense. He did so with Munroe, Emerson's own publisher, who did little to publicize the book. Its failure put Thoreau into debt that took years to pay off, and Emerson's flawed advice caused a schism between the friends that never entirely healed.

In August of 1846, Thoreau briefly left Walden to make a trip to Mount Katahdin in Maine, a journey later recorded in "Ktaadn," the first part of The Maine Woods.

Thoreau left Walden Pond on September 6, 1847. Over several years he worked off his debts and also continuously revised his manuscript. In 1854 he published Walden, or Life in the Woods, recounting the two years, two months and two days he had spent at Walden Pond. The book compresses that time into a single calendar year, using the passage of four seasons to symbolize human development. Part memoir and part spiritual quest, Walden at first won few admirers, but today critics regard it as a classic American book that explores natural simplicity, harmony, and beauty as models for just social and cultural conditions.

After Walden: 1850s
In 1851, Thoreau became increasingly fascinated with natural history (what we would now call science) and travel/expedition narratives. In 1851 he read avidly on the subject, particularly botany, and would often transcribe passages from the books he was reading into his journal. He greatly admired William Bartram, and Charles Darwin's Voyage of the Beagle.

This interest increasingly became evident in his work and journals. He began a project of taking increasingly detailed observations of Concord, recording everything from the ways fruit would ripen over time, to the fluctuating depths of Walden Pond, to the days that certain birds would migrate. The point of his frustrating task was, in his words, to "anticipate" nature.

He became a land surveyor, "travelling a good deal in Concord," and writing natural history observations about the 26 mile² (67 km²) township in his Journal, a two-million word document he kept for 24 years. His observations, far more objective than his previous journals, became so numerous that he began to take a separate natural history notebook for them.

These observations became the source for all of Thoreau's late natural history essays, such as Autumnal Tints, The Sucession of Trees, and Wild Apples, an essay bemoaning the destruction of indigenous and wild apple species.

Until recently, Thoreau's scientific interests and pursuits were dismissed by critics as amateur and sloppy science coupled with a declined prose style. Only recently, with the 1993 publication of Faith in a Seed — a collection of not just his late natural history essays but also including the first publication of his unfinished manuscripts — has it become apparent that Thoreau had accomplished something important. In "Faith," he demonstrated by observation, experimentation and analysis, how 99 percent of forest seeds are dispersed; and how forests change over time, and regenerate after fire or human destruction.

Thoreau worked at his family's pencil factory in 1837-38, 1844, and 1849-50. He had a natural gift for mechanics. According to Henry Petroski, Thoreau discovered how to make a good pencil out of inferior graphite by using clay as the binder; this invention improved upon graphite found in New Hampshire in 1821 by Charles Dunbar. Later, Thoreau converted the factory to producing plumbago, used to ink typesetting machines. Frequent contact with minute particles of graphite may have weakened his lungs.

He traveled to Quebec once, Cape Cod twice, and Maine three times; these landscapes inspired his "excursion" essays, A Yankee in Canada, Cape Cod, and The Maine Woods, in which travel intineraries frame his thoughts about geography, history and philosophy. Other travels took him southwest to Philadelphia and New York City in 1854, and west across the Great Lakes region in 1861, visiting Buffalo, Detroit, Chicago, Milwaukee, and St. Paul.

Hailed as an early American environmentalist, Thoreau wrote essays on autumnal foliage, the succession of forest trees, and the dispersal of seeds, collected in Excursions. Scientists regard these works as anticipating ecology, the study of interactions between species, places, and seasons. He was an early advocate of recreational hiking and canoeing, of conserving natural resources on private land, and of preserving wilderness as public land. Thoreau was also one of the first American supporters of Darwin's theory of evolution. Although he was not a strict vegetarian, he ate relatively little meat and advocated vegetarianism as a means of self-improvement.

Last years and death
Thoreau first contracted tuberculosis in 1835 and suffered from it sporadically over his life. In 1859, following a late night excursion to count the rings of tree stumps during a rain storm, he became extremely ill. His health declined over three years with brief periods of remission, until he eventually became bedridden. Recognizing the terminal nature of his disease, Thoreau spent his last years editing, rewriting, and organizing his unpublished works, particuarly The Dispersion of Seeds, and petitioning publishers to produce his essays and books.

He also maintained correspondences and his journals until he became too weak, after which he would dictate to his sister. His friends' letters and journals are filled with both alarm at his diminished appearance and impending death, as well as fascination with Thoreau's tranquility with his situation. When a friend asked him in his last weeks whether he had made his peace with God, Thoreau responded quite simply: "We've never quarreled."

Thoreau died of tuberculosis in 1862 and was buried at Sleepy Hollow Cemetery. Emerson wrote the eulogy spoken at his funeral. Thoreau's best friend Ellery Channing published his first biography, Thoreau the Poet-Naturalist, in 1873, and Channing and another friend Harrison Blake edited some poems, essays, and journal entries for posthumous publication in the 1890s.

Thoreau's three-million-word Journal, often mined but largely unpublished at his death, appeared in 1906 and helped to build his modern reputation. It is currently being reproduced in a multi-volume set. Today Thoreau is regarded as one of the foremost American writers, both for the modern clarity of his prose style and the prescience of his views on nature and politics. His memory is honored by the international Thoreau Society, the oldest and largest society devoted to an American author.

Criticisms
Thoreau was not without his critics. Scottish author Robert Louis Stevenson judged Thoreau's endorsement of natural simplicity over the tangles of modern society to be a mark of effeminacy: "...Thoreau's content and ecstasy in living was, we may say, like a plant that he had watered and tended with womanish solicitude; for there is apt to be something unmanly, something almost dastardly, in a life that does not move with dash and freedom, and that fears the bracing contact of the world. In one word, Thoreau was a skulker. He did not wish virtue to go out of him among his fellow-men, but slunk into a corner to hoard it for himself. He left all for the sake of certain virtuous self-indulgences."

However, English novelist George Eliot, writing in the Westminster Review, characterized such critics as uninspired and narrow-minded: "People—very wise in their own eyes—who would have every man's life ordered according to a particular pattern, and who are intolerant of every existence the utility of which is not palpable to them, may pooh-pooh Mr. Thoreau and this episode in his history, as unpractical and dreamy." Throughout the 19th century, Thoreau was dismissed as a cranky provincial, hostile to material progress. In a later era, his devotion to the causes of abolition, Native Americans, and wilderness preservation have marked him as a visionary.

Famous persons influenced
Thoreau's writings had far reaching influences on many public figures. Political Leaders and reformers like Mahatma Gandhi, President John F. Kennedy, Civil rights activist Rev. Martin Luther King, Jr., Supreme Court Justice William O. Douglas, and Russian author Leo Tolstoy all spoke of being strongly affected by Thoreau's work, particularly On the Duty of Civil Disobedience. So did many artists and authors including Edward Abbey, Willa Cather, Marcel Proust, William Butler Yeats, Sinclair Lewis, Ernest Hemingway, E. B. White and Frank Lloyd Wright and naturalists like John Burroughs, John Muir, Edwin Way Teale, Joseph Wood Krutch and David Brower. Anarchist and feminist Emma Goldman also appreciated Thoreau, and referred to him as "the greatest American anarchist".

Trivia
One of the most famous quotes often mistakenly attributed to either Thomas Jefferson or Thomas Paine, "That government is best which governs least", actually came from Henry David Thoreau in On the Duty of Civil Disobedience. Thoreau was paraphrasing the motto of The United States Magazine and Democratic Review, "The best government is that which governs least."