It’s not a particularly fresh notion to say that Walt Whitman and Emily Dickinson represent a sort of yin and yang of American literature, or that they are the progenitors of the two main strands of American poetry’s DNA. Whether it’s true or not, the notion just seems to satisfy that human need to reduce complex issues to either/or propositions. And certainly in this age of irony and reverse-irony and un-ironic irony, it can be argued that those two strands have been tied off and cauterized for good, but the influences of Whitman and Dickinson can still be seen, if not felt.
Just look at random pages from their respective work and you'll see the dichotomy. Walt has those long, looping lines, while Miss Emily’s are short—usually no more than eight syllables, and as tightly metered as a Puritan hymn (many of her poems can be sung to the tune of “The Yellow Rose of Texas.” Try “Because I Could Not Stop for Death ;” It works eerily well).
In that dualist construct, Walt (I call him Walt because I imagine he would want me to --“Please! Call me Walt!” I also imagine he would be the kind of guy whose every word, no matter how mundane, would end in an exclamation point --“It’s not the heat! It’s the humidity!”) represents the sprawling, boisterous, long-limbed, inclusive nature of our national character. He may not be the mob, but he'd help fill out its ranks. Miss Emily, on the other hand, is the embodiment of a darker, more contemplative sensibility. It is the insular and the fragmented, the frightened, insecure child in our collective (sub)conscious. I can easily picture Miss Emily, had she not discovered her vocation for poetry, making a career of slipping a pinch of arsenic to a few dozen gentlemen lodgers; just as I could see ol' Walt making a mint selling used horseless carriages.
In the end, the Whitman-and-Dickinson-as-America thesis is fine as far as it goes, but when you get right down to it, the two poets represent not two ways of being American, but two ways of being human. It's the old gnostic split between the mind and the body, the spiritual and the profane, the outward and the inward. We can choose sides all we want, but the fact is that both Miss Em' and good ol' Walt, for good and ill, are in all of us.
The Complete Poems of Emily Dickinson / edited by Thomas H. Johnson
The Letters of Emily Dickinson  / Thomas H. Johnson and Theodora Ward, editors
Glenda Jackson, Meryl Streep, Sharon Stone among others read Fifty Poems by Emily Dickinson, Volume I  , then they take a deep breath and read another Fifty Poems by Emily Dickinson, Volume II .
The Essential Whitman  / selected and with an introduction by Galway Kinell
The Complete Poems / Walt Whitman  / edited by Francis Murphy
Leaves of Grass  [sound recording], read by Noah Waterman