Originally published in 1855, the work started as a collection of 12 unnamed poems. However, Whitman spent most of his life writing and re-writing Leaves of Grass, resulting in many different editions published throughout his life. The final collection, which is recorded here, is a compilation of about 400 poems separated into 35 books. Among some of the best known poems contained in this work are "O captain! My captain!", "I sing the body electric", and "Song of Myself".