Okay, so Walt Whitman didn't invent the exclamation point, and he wasn't the first poet to use it in the opening line of a poem. But his poems include it so often that he really made it his own. Here are just a few examples of first lines from his poems (there are many more!):
"To thee, old cause!" "Earth! My likeness!" "Pioneers! O Pioneers!" "O captain! My captain!" "Joy, shipmate, joy!"
Also, we can't forget that Whitman loved to write about America. To quote ourselves (we love doing that): "Whitman was the self-appointed bard of American life, singing of men and women, North and South, soaring ideals, and the gritty reality of the physical world. His poetry reflected the truth of daily life." "Beat! Beat! Drums!" is all that that and a bag of Cracker Jacks.