What contribution did Whitman make to American and European poetry creation?

Whitman's poems not only give people a strong shock in content, but also have great innovations in form. He used the spoken language of the people to break the traditional rhythm of poetry and create a new rhythmic style of free poetry, thus enhancing the expressive force of poetry and establishing the status of free poetry, which had a far-reaching impact on later poetry creation in the United States and Europe. Leaves of Grass has thus become an important milestone in modern American literature and a shining example of American national literature.