Henry David Thoreau was an American author, poet, philosopher, abolitionist, naturalist, tax resister, development critic, surveyor, historian and leading transcendentalist. He is best known for his book Walden, a reflection upon simple living in natural surroundings, and his essay Resistance to Civil Government (also known as Civil Disobedience), an argument for disobedience to an unjust state.

Thoreau’s books, articles, essays, journals, and poetry total over 20 volumes. Among his lasting contributions were his writings on natural history and philosophy, where he anticipated the methods and findings of ecology and environmental history, two sources of modern day environmentalism.