Henry David Thoreau , ( born July 12 , 1817 , Concord , Massachusetts , U.S. —died May 6 , 1862 , Concord ) American essayist , poet , and practical philosopher , renowned for having lived the doctrines of Transcendentalism as recorded in his masterwork , Walden ( 1854 ) , and for having been a vigorous advocate of civil liberties , as evidenced in ...