The central archetype of classic American literature--somewhat related to the Noble Savage--is the American Adam.
R.W.B. Lewis. The American Adam: Innocence, Tragedy, and Tradition in the Nineteenth Century. Chicago: U of Chicago Press, 1955.
Leo Marx. The Machine in the Garden: Technology and the Pastoral Ideal in America. London: Oxford UP, 1973.
Pastoral refers to a genre of European literature whose basic design outlines the longing of someone trapped in the complexities of civilization and "modern" life to withdraw from the city and retreat to a simpler, less complicated existence located in an idealized natural setting.
This pastoral literature eventually became linked to the quest for a perfect life of innocence and simplicity: the Golden Age; the Garden of Eden.
Combining some observations on the pastoral by M.H. Abrams and Northrup Frye, one can say that the search for the pastoral landscape becomes a journey in search of healing and innocence and rebirth: the seeker leaves behind the civilized world and enters the "Green World" of the pastoral, a place of transformation and regeneration and spiritual rebirth. This rebirth is not necessarily easy: it may require the overcoming of obstacles, some sort of "dying" away from society, or a loss of some aspect of the questor. In the pastoral, however, the tone is ultimately optimistic and hopeful. The questor, having been energized and reborn, returns to civilization but is now operating on a higher spiritual plane.
Importantly, this quest is not necessarily successful. If there is pastoral literature, there is also ANTI-pastoral literature. Two forces operate to threaten the pastoral quest: (a) the death that nature implicitly holds in store for us all, and (b) the evil within each human soul. So anti-pastoral authors argue against the notion that humans can reach the Garden. The tone is nostalgic or elegiac.
NOW: On to America.
When Columbus landed in America, his discovery of a seemingly "empty" landscape (the Indians notwithstanding) seemed to give a real existence to what had previously been the realm of myth. The "fresh green breast of the New World," as Fitzgerald calls it at the end of The Great Gatsby, became the repository of all sorts of fantasies and longings for a perfect garden that endure down to the present day. The dominant metaphor that came to describe America was that it was a gardenin fact, THE Gardenof Eden.
If America is the Garden, then who lives here? Adam, of course (and sometimes Eve). So the classic American character is a naif, the American Adam; the central American story is the depiction of how this innocent encounters the world. Most American writers take the pastoral quest for the Garden and mock it or show that it is an unrealistic, hopeless longing (as Fitzgerald reminds us on the last page of Gatsby and as Melville shows in Billy Budd).
Emerson, Thoreau, and Whitman present a positive side to the American Adam; Poe, Hawthorne, and Melville present the negative side.