I think you are off to a good start with some powerful quotes and examples. I do see the need in your first body paragraph to connect those quotes to your thesis or prompt on how the American dream is still alive or possible. Analyze those quotes and examples to show how or why they support the thesis and paragraph's topic sentence.
The best way to conclude any paragraph, is it to bring together and reiterate the paragraph's main idea as shown through your examples. This is called synthesis. Restate or recap the main idea of your essay (which should also support your topic sentence) by having a concluding statement that ends the paragraph. You are then ready to make a transition to your next paragraph and start a new topic.
I know you probably haven't revised and edited yet, and this is probably your rough draft. I do see some errors in punctuation and especially your verb tense. Make sure your verbs are all in the same tense, either past or present. Past tense is probably the easiest way to write the essay.
I would also like to suggest a never fail technique in finding errors--Read your writing slowly out loud. You will be surprised with what you catch. Make sure you read it exactly how your wrote it, though.
I hope this helps, and good luck!