What is America's epic?

The Twitter question du jour is: What is America's epic? That is, what is to America what the Iliad is to Greece, Ulysses is to Ireland, and Don Quixote to Spain?

My first thought was Moby-Dick, which is a pretty common answer. But I'll take The Scarlet Letter instead:

1. It is accessible yet difficult, engaging, and deeply moral.
2. It's part of our explicit national consciousness in a way that Moby-Dick and most other contenders are not.
3. More people have actually read it than Moby-Dick and most other contenders. (Let me be clear that I also have not read more than 1/5 of Moby-Dick, but I have read many other classic American novels.)
4. It is, arguably, an origin story about American morals and values. (The frame of the novel is underrated.)
5. And it is a story about the transmission of values and character. A good epic should have at least one main character who is a child, right?

I'll put The Great Gatsby in second place:

1. There are explicit visions of American values and character traits. Think of the note about American physique and sports when Gatsby is leaning out of his fancy car or the note about how "Americans, while occasionally willing to be serfs, have always been obstinate about being peasantry."
2. It's still quite famous. Plenty of Americans have read it (though I strongly suspect that far fewer high schoolers read it these days).
3. It is built around a journey from the Midwest to the East and back.

I haven't seen anyone mention East of Eden yet, but I'd put it somewhere in the 5 or 10 best answers to this question.