Think about the great depression as a story line in American history. Identify three or four events/people/turning points where that topic is especially interesting or important. Be sure to space those points out over time. And then write an essay in which you use those events or people to tell a story about how America changed during that span of time. Not the whole story, just a story, centered on your chosen topic.
All applicants go through a series of tests that check their level of English and knowledge of formatting styles. The applicant is also required to present a sample of writing to the Evaluation Department. If you wish to find out more about the procedure, check out the whole process.