Final answer:
The writer who is NOT from Georgia is Harriet Beecher Stowe.
Step-by-step explanation:
From the given options, the writer who is NOT from Georgia is C. Harriet Beecher Stowe. Harriet Beecher Stowe was born in Connecticut and is best known for her novel 'Uncle Tom's Cabin', which played a significant role in shaping public opinion about slavery in the United States. On the other hand, A. Erskine Caldwell, B. Flannery O'Connor, and D. Margaret Mitchell are all writers from Georgia.