Answer:
Slavery was very important to both the American economy and the culture of the southern states. While most textile factories were located in northern states, their cotton supplies came from southern states. The cotton production of the southern states was also exported to many countries (was America's #1 export), although it made the southern economies extremely dependent on their agriculture production.
The combination of having an agricultural product whose world demand was very high plus factories that processed the product and made finished goods, greatly contributed to the emergence of the US as a great economic power.