Walter Whitman Jr. was an American poet, essayist, and journalist; he also wrote two novels. He is considered one of the most influential poets in American literature and world literature. Whitman incorporated both transcendentalism and realism in his writings and is often called the father of free verse. His work was controversial in his time, particularly his 1855 poetry collection Leaves of Grass, which was described by some as obscene for its overt sensuality.