Thoreau is considered one of the most influential figures in American thought and literature. A supreme individualist, he championed the human spirit against materialism and social conformity. His most famous book, Walden (1854), is an eloquent account of his experiment in near-solitary living in close harmony with nature; it is also an expression of his transcendentalist philosophy.
Thoreau grew up in Concord and attended Harvard, where he was known as a serious though unconventional scholar. During his Harvard years he was exposed to the writings of Ralph Waldo Emerson, who later became his chief mentor and friend. After graduation, Thoreau worked for a time in his father's pencil shop and taught at a grammar school, but in 1841 he was invited to live in the Emerson household, where he remained intermittently until 1843. He served as handyman and assistant to Emerson, helping to edit and contributing poetry and prose to the transcendentalist magazine, The Dial.
In 1845 Thoreau built himself a small cabin on the shore of Walden Pond, near Concord; there he remained for more than two years, "living deep and sucking out all the marrow of life." Wishing to lead a life free of materialistic pursuits, he supported himself by growing vegetables and by surveying and doing odd jobs in the nearby village. He devoted most of his time to observing nature, reading, and writing, and he kept a detailed journal of his observations, activities, and thoughts. It was from this journal that he later distilled his masterpiece, Walden. The journal, begun in 1837, was also the source of his first book, A Week on the Concord and Merrimack Rivers (1849), as well as of his posthumously published Excursions (1863), The Maine Woods (1864), Cape Cod (1865), and A Yankee in Canada (1866).
One of Henry David Thoreau's most important works, the essay "Civil Disobedience" (1849), grew out of an overnight stay in prison as a result of his conscientious refusal to pay a poll tax that supported the Mexican War, which to Thoreau represented an effort to extend slavery. Thoreau's advocacy of civil disobedience as a means for the individual to protest those actions of his government that he considers unjust has had a wide-ranging impact—the British Labor movement, the passive resistance independence movement led by Gandhi in India, and the nonviolent civil-rights movement led by Martin Luther King Jr. in the United States.