Walt Whitman 
Leaves of Grass 

Leaves of Grass is a poetry collection by the American poet Walt Whitman (1819–1892). Though the first edition was published in 1855, Whitman spent most of his professional life writing and re-writing Leaves of Grass, revising it multiple times until his death. This resulted in vastly different editions over four decades—the first a small book of twelve poems and the last a compilation of over 400.