The speaker calls the Captain “father,” another sign of his deep respect. Here Lincoln is metaphorically the father of the national family as well as the captain of the ship of state.

Compare Whitman’s “As I Ebb’d With the Ocean of Life,” in which he portrays his native shore as a “father” to which he clings:

I throw myself upon your breast my father,
I cling to you so that you cannot unloose me,
I hold you so firm till you answer me something.

Some critics have suggested a link between these father figures and Whitman’s actual father, Walter Whitman, Sr., with whom the poet had a troubled relationship. Whitman, Sr. died shortly after the first edition of Leaves of Grass appeared in 1855. In his reading of “As I Ebb’d,” R. W. French comments:

As is often pointed out, Whitman generally shows little sympathy for father figures; the best-known such figure in his poetry, for example, is the distant and fearsome father of “There Was a Child Went Forth,” a representation of power, injustice, and oppression. It is a sign of the new-found humility in this poem that the poet can plead as he does with the “father,” the land.

Ties together the images of “exulting” crowds from stanza 1 and ringing bells from stanza 2.

Whitman suggests that celebration of the Union victory should continue despite grief over Lincoln’s death. In the final lines he seems to take the burden of mourning onto his own shoulders, as a kind of poet-spokesman for his nation.

Supporters of Lincoln are imagined as an “eager” crowd on shore, awaiting the Captain’s arrival.

Though many Union supporters, including freed slaves, embraced their President as a hero at the end of the war, the national mood even in the North was more divided and complex than Whitman suggests. Historian Sarah Pruitt describes the scene of Lincoln’s final speech:

A cheering, singing crowd of hundreds gathered on the White House lawn, with rolls of intense applause greeting Lincoln’s appearance at the window of the second-floor balcony in the North Portico. The president waited several minutes for the din to subside….

Lincoln had prepared this speech carefully. Though he began on a joyful note—“We meet this evening, not in sorrow, but in gladness of heart. The evacuation of Petersburg and Richmond and the surrender of the principal insurgent army, give hope of a righteous and speedy peace”—and promised a day of “national thanksgiving” he proceeded directly to a reminder that the nation now faced a task “fraught with great difficulty,” that of “re-inauguration of the national authority—reconstruction.”

The formerly jubilant crowd fell silent as Lincoln delivered his remarks, which were far from the celebratory address they had expected. [History.com]

Whitman heard the news of Lincoln’s death while staying with his mother in Brooklyn. He recalled his reaction in Specimen Days (1882):

The day of the murder we heard the news very early in the morning. Mother prepared breakfast—and other meals afterward—as usual; but not a mouthful was eaten all day by either of us. We each drank half a cup of coffee; that was all. Little was said. We got every newspaper morning and evening, and the frequent extras of that period, and pass’d them silently to each other.

https://youtu.be/JZYe_M1itjI?t=19m

The heroic captain in this section prefigures the martyred hero of Whitman’s “O Captain! My Captain!” (1865), an elegy for the assassinated Abraham Lincoln.