The previous post was quite strong. I would say that there is a parallel between the maturation and growth of the country and the literature it produced. The literature produced at the time of the Colonial period was dominated by a fear or belief in God and human dimensions dwarfed into this context. The writing was not very complex in terms of thematic development and proved to be moralistic, in trying to teach morals to readers. This makes sense as the colonies were struggling to survive both literally and figuratively. In a literal sense, the journey over was harrowing and many of the conditions found in the new world were equally challenging. Once entrenched into the new setting, the battles between the French and Indians, and then the British began to set the stage for a new identity that was formed over time. The literature that was produced in the era of Transcendentalism reflects this growth and maturation of identity. The complexities of human motivation and action were examined in works like Hawthorne and Melville. At the same time, a new relationship between God and the individual was being carved out where there was a questioning as to how both operated within one another and towards each other. There was a thematic exploration of how to integrate the subjective experience in writing through emotions and making it a very reflective process for both reader and author. This shows a growth and maturation, similar to the country growing in literal and figurative terms.
Good question. To understand the literature of a period, you have to know what's happening during the period.
Think about what's going on during the Discoveries/Colonial periods, and you'll quickly know what kinds of things were written. People were exploring and colonizing and settling, and they were keeping journals. Thus we have writings such as Bartolome de Las Casas' Brief Account of the Devastation of the Indies, John Smith's Journal and William Bradford's Of Plymouth Plantation. Journals, diaries, sermons (such as "Sinners in the Hands of an Angry God"), meditational poetry (such as the works of Anne Bradstreet) are all common genres of literature for this time. Think of it as being generally more practical and useful than creative.
The word renaissance, of course, means "rebirth." There have been periods of such rebirth in all places, most notably the English Renaissance of the 16th century. The American Renaissance happens after the country has begun to settle in after its initial "growing pains," when people can do more than just try to survive, figuratively speaking. Life is still hard, of course, but there is now opportunity to write about beauty and life, and reason. We see poetry (most notably Walt Whitman), novels (such as the classics The Scarlet Letter and Moby Dick), and reflections on reason and self (primarily from Emerson and Thoreau in the form of essays and journal). We also have the first short stories from Washington Irving and Edgar Allan Poe. The creativity and diversity of genres is testament to the rebirth of creativity after the struggles of settlement and the battle for independence.
This period is relatively short-lived, however, as the next driving force of history--the Civil War--changes the dynamics and genres of literature to a more practical bent. The literature of those early periods is helpful for historical accuracy and understanding. The genres of the American renaissance, in particular, though, have carried through to the present.