Leaves of Grass is a poetry collection by American poet Walt Whitman. First published in 1855, Whitman spent most of his professional life writing and rewriting Leaves of Grass, revising it multiple times until his death. There have been held to be either six or nine individual editions of Leaves of Grass, the count varying depending on how they are distinguished.[2] This resulted in vastly different editions over four decades—the first edition being a small book of twelve poems, and the last, a compilation of over 400.

(Source: Wikipedia)