A beloved and more modern poet who nobody has yet mentioned is Mary Oliver, who just passed away last year. Probably her most famous poem is this one:

Wild Geese

You do not have to be good.

You do not have to walk on your knees

for a hundred miles through the desert repenting.

You only have to let the soft animal of your body

love what it loves.

Tell me about despair, yours, and I will tell you mine.

Meanwhile the world goes on.

Meanwhile the sun and the clear pebbles of the rain

are moving across the landscapes,

over the prairies and the deep trees,

the mountains and the rivers.

Meanwhile the wild geese, high in the clean blue air,

are heading home again.

Whoever you are, no matter how lonely,

the world offers itself to your imagination,

calls to you like the wild geese, harsh and exciting —

over and over announcing your place

in the family of things.

Hi Meysam,

I would add to Jamie's list two earlier female poets from the American colonial period: Anne Bradstreet, a 17th century English settler in New England, and Phillis Wheatley, a young Senegambian woman enslaved in Boston in the 1760s and 1770s. They were the first women in what would become the United States to publish poetry in English.

We should also mention Maya Angelou, who was a writer in several genres including poetry.

(By Ogden Nash)

It is common knowledge to every schoolboy and even every Bachelor of Arts,

That all sin is divided into two parts.

One kind of sin is called a sin of commission, and that is very important,

And it is what you are doing when you are doing something you ortant,

And the other kind of sin is just the opposite and is called a sin of omission

  and is equally bad in the eyes of all right-thinking people, from

  Billy Sunday to Buddha,

And it consists of not having done something you shuddha.

I might as well give you my opinion of these two kinds of sin as long as,

  in a way, against each other we are pitting them,

And that is, don't bother your head about the sins of commission because

  however sinful, they must at least be fun or else you wouldn't be

  committing them.

It is the sin of omission, the second kind of sin,

That lays eggs under your skin.

The way you really get painfully bitten

Is by the insurance you haven't taken out and the checks you haven't added up

  the stubs of and the appointments you haven't kept and the bills you

  haven't paid and the letters you haven't written.

Also, about sins of omission there is one particularly painful lack of beauty,

Namely, it isn't as though it had been a riotous red-letter day or night every

  time you neglected to do your duty;

You didn't get a wicked forbidden thrill

Every time you let a policy lapse or forget to pay a bill;

You didn't slap the lads in the tavern on the back and loudly cry Whee,

Let's all fail to write just one more letter before we go home, and this round

  of unwritten letters is on me.

No, you never get any fun

Out of things you haven't done,

But they are the things that I do not like to be amid,

Because the suitable things you didn't do give you a lot more trouble than the

  unsuitable things you did.

The moral is that it is probably better not to sin at all, but if some kind of

  sin you must be pursuing,

Well, remember to do it by doing rather than by not doing. 

Hi Meysam, I am not very famliiar with American English poets, but you may enjoy this one by Dylan Thomas a Welsh poet. One of his most famous poems and one my favourites is Fern Hill (I've left out one the penultimate verse as it wouldn't all fit).

Now as I was young and easy under the apple boughs

About the lilting house and happy as the grass was green,

     The night above the dingle starry,

          Time let me hail and climb

     Golden in the heydays of his eyes,

And honoured among wagons I was prince of the apple towns

And once below a time I lordly had the trees and leaves

          Trail with daisies and barley

     Down the rivers of the windfall light.

And as I was green and carefree, famous among the barns

About the happy yard and singing as the farm was home,

     In the sun that is young once only,

          Time let me play and be

     Golden in the mercy of his means,

And green and golden I was huntsman and herdsman, the calves

Sang to my horn, the foxes on the hills barked clear and cold,

          And the sabbath rang slowly

     In the pebbles of the holy streams.

All the sun long it was running, it was lovely, the hay

Fields high as the house, the tunes from the chimneys, it was air

     And playing, lovely and watery

          And fire green as grass.

     And nightly under the simple stars

As I rode to sleep the owls were bearing the farm away,

All the moon long I heard, blessed among stables, the nightjars

     Flying with the ricks, and the horses

          Flashing into the dark.

Everyone is giving you very good lists of names of our most beloved American poets. As for what we read in high school, the books that I had to read included <em>The Adventures of Huckleberry Finn</em> by Mark Twain, <em>The Scarlet Letter</em> by Nathaniel Hawthorne, <em>Moby Dick</em> by Herman Melville, <em>A Tale of Two Cities</em> by Charles Dickens, <em>The Great Gatsby</em> by F. Scott Fitzgerald, <em>Of Mice and Men </em>and <em>The Pearl </em>by John Steinbeck, maybe <em>The Old Man and the Sea</em> and <em>A Farewell to Arms</em> and <em>The Sun Also Rises</em> and <em>For Whom the Bell Tolls</em> all by Ernest Hemingway, <em>Jane Eyre</em> and <em>Wuthering Heights</em> by the Bronte sisters, <em>the Odyssey </em>by Homer, and lots of Shakespeare's plays including Julius Caesar, Hamlet, Romeo and Juliet, A Midsummer's Night Dream, etc. I am sure I have forgotten to mention many other titles, but this should get you started.