From 1837 to 1861, Thoreau kept a Journal that began as a conventional record of ideas, grew into a writer's notebook, and eventually became the principal imaginative work of his career. The source of much of his published writing, the Journal is also a record of both his interior life and his monumental studies of the natural history of his native Concord, Massachusetts. In contrast to earlier editions, the "Princeton Edition" reproduces the Journal in its original and complete form, in a reading text that is free of editorial interpolations but keyed to a comprehensive scholarly apparatus. This volume spans a period of rapid change in Thoreau's life and literary career, including the publication of his first book and a crisis in his friendship with Emerson, during which the Journal assumes its mature form as the extensive, regular, and dated record of his studies of and reflections on the natural and human life of the Concord region.