Whitman's work breaks the boundaries of poetic form and is generally prose-like. He also used unusual images and symbols in his poetry, including rotting leaves, tufts of straw, and debris. He also openly wrote about death and sexuality, including prostitution. He is often labeled as the father of free verse, though he did not invent it.
Whitman wrote in the preface to the 1855 edition of Leaves of Grass, "The proof of a poet is that his country absorbs him as affectionately as he has absorbed it." He believed there was a vital, symbiotic relationship between the poet and society. This connection was emphasized especially in "Song of Myself" by using an all-powerful first-person narration. As an American epic, it deviated from the historic use of an elevated hero and instead assumed the identity of the common people. Leaves of Grass also responded to the impact that recent urbanization in the United States had on the masses.