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 poems.
The poems of Leaves of Grass are loosely connected and each represents Whitman’s celebration of his philosophy of life and humanity. … Influenced by Ralph Waldo Emerson and the Transcendentalist movement, itself an offshoot of Romanticism, Whitman’s poetry praises nature and the individual human’s role in it. (Wikipedia)