The Complete Poems of Walt Whitman gathers the evolving work of a poet who made the self expansive enough to contain a democracy. The center is Leaves of Grass, first published in 1855 and revised across multiple editions until Whitman's death.
Author
Walt Whitman

Frequently Cited
“I celebrate myself, and sing myself, And what I assume you shall assume, For every atom belonging to me as good belongs to you”
“Do I contradict myself? Very well then I contradict myself, (I am large, I contain multitudes”
“I sound my barbaric yawp over the roofs of the world”