I believe the answer is democracy ^^
Before the invention of the cotton gin only long thread cotton could be profitably grown. The long thread cotton could only be grown in a limited geographic locations.
The cotton gin allowed short thread varieties of cotton to be profitably grown throughout the south. This increase in cotton production lead to the expression that cotton is king. The southern plantation owners became rich. The economy of the south became depended on cotton.
In the north the availability of large amounts of now relatively cheap cotton made textile mills a possibility in the north. These textile mills utilizing cotton from the south were the foundation of the industrialization of the north, providing great wealth and attracting immigrants from Europe.
The cotton gin changed the economy of the south to a mainly agriculture economy based on cotton and slavery.
The cotton gin changed the economy of the north to a mainly industrial factory based economy requiring educated workers from European nations.
The southern economy wanted low import duties to purchase manufactured goods with their agricultural products.
The northern economy wanted high import duties to protect their new industries from European competition
The answer is Both A and B.
