The Coastal Plain region of Virginia.
A, Slaves provided much of the labor on plantations that grew cash crops would be the answer I would go with. Most slaves worked in crop fields, and iron working didn't become prominent in the US until the industrial revolution about 10 years after the Civil War. I cannot say I'm 100% certain, but the others to me don't seem to make sense when looking at the situation.
If this is true or false, this would be true.
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