South - One crop Cotton. Eli Whitney Cotton Gin streamlined cotton in being able to remove seeds more quickly. The South was not able to sell cotton to other countries. Cotton was only able to be sold to the Northern textile industry.
The south had no industry - there was no manufacturer of ammunitions, steel, or any other manufacturing. The South started its own iron works when the vote for secession went into place.
The South wanted to export cotton.
In the year prior to the war the South exported over three million bales of cotton to overseas customers.
Sorry, that's simply not true. Here's a chart of cotton exports from 1815 to 1860. See Figure 2. In 1860 exports were around $200M, which was a LOT of money at the time.
http://eh.net/encyclopedia/the-economics-of-the-civil-war/
People often get confused and think there were restrictions or tariffs on exports. There weren't, these being specifically prohibited by the Constitution.
Au contraire. Surely you've heard of "King Cotton"? The combined wealth of the antebellum south, and some of the wealthiest men in America was concentrated by a couple dozen plantation owners. They sold lots of cotton.
Interestingly, at the advent of the war the south sought to maximize their profits by jamming up the textile markets through a cotton embargo. It was expected that Great Britain, their largest customer, would realize the threat to their industries and business and cozy up.
Instead what happened was tons of rotting cotton on the wharfs and GB finding alternative sources for cotton from Egypt and elsewhere.
That is not true. Cheap cotton made the Industrial Revolution possible. And slavery was central to that chain as the raw material had to be cheap and abundant to make the scale of the Industrial Revolution possible. It also made cotton fabric cheap and abundant for mass consumption all over the world, including in Africa were it was very popular.
So, in a sense everyone who has benefitted from the Industrial Revolution benefitted from slavery.