If you were ever forced to read poetry in high school, chances are good that you read Walt Whitman at some point. "I Hear America Singing," from Whitman's groundbreaking collection Leaves of Grass is a love letter to his country, and it's become something like the national anthem of poems. Whitman is inarguably America's greatest poet, and this is his celebration of the place that made him. Like most great artists, however, Whitman was not always celebrated during his life. Leaves of Grass was controversial for its time, condemned frequently for its overt and hidden allusions to sexuality, in particular Whitman's love for other men. He had many close relationships with male admirers, including a friendship with Oscar Wilde, and this was expressed in his poems. One of his most famous works, "Song of Myself," even includes a reference to oral sex, and the 1860 edition of Grass included a group of poems called "Calamus" promoted and reveled in "adhesive love," a now outdated term used to describe same-sex attraction. The book was often banned, but it's now recognized as a landmark achievement in both American poetry and poetry as a movement; Whitman is called "the father of free verse" for his long, lyrical lines that didn't adhere to poetic rules and could more fully embrace the rambling ways of nature and thought. He was free and open with his sexuality at a time when American societal strictures were harshly anti-gay.