One's-self I sing, a simple separate person,
Yet utter the word Democratic, the word En-Masse.
Of physiology from top to toe I sing,
Not physiognomy alone nor brain alone is worthy for the Muse, I say
the Form complete is worthier far,
The Female equally with the Male I sing.
Of Life immense in passion, pulse, and power,
Cheerful, for freest action form'd under the laws divine,
The Modern Man I sing.
That this line should open the work  Leaves of Grass  is appropriate; Whitman was adamant that men and women are equal, and that the ideas of his poems applied to and could be appreciated by men and woman equally; this made Whitman a favorite of the great feminist novelist and poet Erica Jong. Whitman speaks to everybody and lets us know that up front. 
 Later in the work, in “Song of Myself,” he declares that he is the poet of the female as well as the male, and tells “any man of woman” to “let their soul stand cool and composed before a million universes.” Compare the Holy Quran, 33:35, which equally goes out of its way to establish an equality of man and woman: 
 The submitting men, the submitting women, the believing men, the believing women, the obedient men, the obedient women, the truthful men, the truthful women, the steadfast men, the steadfast women, the reverent men, the reverent women, the charitable men, the charitable women, the fasting men, the fasting women, the chaste men, the chaste women, and the men who commemorate GOD frequently, and the commemorating women; GOD has prepared for them forgiveness and a great recompense. 
 Of course, Whitman speaks not only of literal equality of men and women, but of a balance between the traditionally female and male aspects of human existence and nature. 

Ones-Self I Sing