Why was slavery important to the economy in the south before the civil war?

It made the South rich in cash crops, consisting of tobacco, cotton, sugar cane, and more.

Explanation:

The slave economy had been very good to American prosperity, due to their forced labor, as well as, long days of work. The South produced 75% of the world's cotton and created more millionaires per capita in the Mississippi River valley than anywhere in the nation. Slaves represented Southern planters' investment, as well as the bulk of their wealth.