Because the speaker expresses his relief that the ship has reached its home port at last and describes hearing people cheering. In the final stanza, the speaker juxtaposes his feelings of mourning and pride. And well that's what makes it elegy, because of the mourning. I hope this helps! :) definition for elegy: a mournful, melancholy, or plaintive poem, especially a funeral song or a lament for the dead.
"O Captain! My Captain" is a mournful poem about Abraham Lincoln.
Explanation:
The poem "O Captain! My Captain!" was written by Walt Whitman shortly after Abraham Lincoln died. It is an elegy, which means it is a sad, mournful poem expressing sorrow and admiration for someone who has passed away.
The whole poem is a metaphor, in the sense the Lincoln's name is never openly mentioned. The speaker uses the captain to represent Lincoln, and the ship to represent the United States. The speaker talks of victory, of the ship coming home safely after going through hardship. What Whitman means by that metaphor is that the nation is happy and safe after the hardship that was the Civil War. Yet, the speaker cannot be happy, for his Captain has died before he could see the ship sail to victory.
