The crowd has gathered on the shore to welcome home the ship and celebrate the victory that has been won. They are eager to celebrate the captain responsible for this great victory.
However, this poem is not really about a captain and a ship. Instead, this poem is about Abraham Lincoln, the captain of America. The battle, then, is the Civil War. The crowd is celebrating the fact that the war has ended, but sadly the captain is not alive to enjoy the victory, as Lincoln was assassinated.