Henry David Thoreau (1817–1862), writer, philosopher, and naturalist, lived in Concord, Massachusetts, most of his life. He won his place in American literature by, as he put it, traveling a good deal in Concord. He made numerous trips to Maine, Cape Cod, and New Hampshire, and also traveled to Quebec, Canada, and Minnesota in an unsuccessful attempt to strengthen his tubercular lungs. Thoreau never married. He read widely and wrote constantly in his journals, using them as sources for lectures, essays, and his books A Week on the Concord and Merrimack Rivers (1849) and Walden (1854). His neighbors knew him as an educated man without an occupation. He worked as a school teacher, as a handyman at Ralph Waldo Emerson's house, and as a tutor.

Thoreau lived for two years in a cabin he built on Emerson's property at Walden Pond. During that time, he also surveyed property, wrote magazine articles, and worked in his father's pencil factory. In 1846 Thoreau spent one night in jail for refusing to pay his poll tax, in protest of the Mexican War (1846–1848). In his essay "Civil Disobedience" (1849), he clarified his position and discussed passive resistance, a method of protest that later was adopted by civil rights activists.

Thoreau's work demonstrates how the abstract ideals of individualism and libertarianism can be effectively instilled in a person's life. His most popular essays during his lifetime were Slavery in Massachusetts and A Plea for Captain John Brown. He was forty-four when he died of tuberculosis at his mother's house in Concord. Sections of his books The Maine Woods and Cape Cod were published after his death.