The south will not be able to maintain its agriculturral output until it developed a new system to replace

Although you have not given any options to choose from or have not provided any background information about the question, I believe the most applicable answer is "Slavery".

Explanation:

Slavery was the main driver of economy in the south as the economy was heavily relying on plantations. Because of this, when the Slavery was abolished, Southern states went to war with the union as they felt their economy and the way of life was threatened.

answer: the ocean

explanation: if you map out 30 n and 40 n latitude, you will get the ocean