Henry David Thoreau (July 12, 1817 - May 6, 1862) was an American author, poet, philosopher, polymath, 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. Among his books, articles, essays, journals, and poetry, much of his lasting contributions are 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. In An Excursion to Canada, Thoreau is critical of what he sees as well as comparative and competitive about the United States. An unusual approach for a man generally critical of the United States for many perceived shortcomings.