Henry David Thoreau (born J. in Concord, Massachusetts, U.S.—died in Concord), American writer, poet, and practical philosopher, best known for living the Transcendentalist principles enshrined in his opus, Walden (1854), and for being a zealous supporter of civil freedoms, as... Thoreau's father was an attorney who became wealthy practicing law. When Henry was young, the family moved to a larger house with more room for Henry to grow up in. He spent his time reading books from the local library instead of playing with his friends. At age 20, he left home to live alone in a small cabin on top of a hill near town. Here he could focus on writing. He published two books during his lifetime: A Week on the Concord & Merrimack Rivers (1849) and Cape Cod (1866). Both were very successful. In addition, many of his essays, poems, and reviews were published in magazines at the time. Thoreau is regarded as one of the founders of environmentalism because of his efforts to protect nature against deforestation and other forms of destruction. His book, Walking (1863), inspired people all over the world to take walks in the countryside and thus promote wildlife conservation. Furthermore, he is also credited with first proposing a national park system as we know it today.