In 1855 Whitman published at his own expense a volume of 12 poems, Leaves of Grass, which he had begun working on probably as early as 1847. Prefaced by a statement of his theories of poetry, the volume included the poem later known as "Song of Myself," in which the author proclaims himself the symbolic representative of common people. Although the book was a commercial failure, critical reviewers recognized the appearance of a bold new voice in poetry. Two larger editions appeared in 1856 and 1860, and they had equally little public success.
Leaves of Grass was criticized because of Whitman's exaltation of the body and sexual love and also because of its innovation in verse form—that it, the use of free verse in long rhythmical lines with a natural, "organic" structure. Emerson was one of the few intellectuals to praise Whitman's work, writing him a famous congratulatory letter. Whitman continued to enlarge and revise further editions of Leaves of Grass ; the last edition prepared under his supervision appeared in 1892.