Henry David Thoreau was an American writer, philosopher, and naturalist born on July 12, 1817. He is best known for his book Walden, which reflects on simple living in natural surroundings. Thoreau spent two years living in a cabin near Walden Pond in Massachusetts, where he observed nature and wrote about his experiences. Thoreau was also an advocate for social reform and civil disobedience. His essay, Civil Disobedience, argues that individuals should not permit governments to overrule their consciences. Thoreau's ideas have influenced various movements, including environmentalism and nonviolent resistance. He died on May 6, 1862.