Walt Whitman is the American poet known for his ambitious exploration of identity in his seminal work, "Leaves of Grass." Through free verse and a distinct voice, Whitman celebrated individuality, the human experience, and the interconnectedness of all people. His poetry often sought to break societal norms, pushing boundaries related to sexuality, democracy, and personal expression. Whitman's approach to poetry had a profound impact on later generations, influencing the trajectory of American literature and solidifying his status as a key figure in the romantic and modernist movements.