make this sound less formal
Suddenly cotton became a lucrative crop and a major export for the South. However, because of this increased demand, many more slaves were needed to grow cotton and harvest the fields. Slave ownership became a fiery national issue and eventually led to the Civil War.
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Cotton, all of a sudden, became a major moneymaker for the South. With this boom in demand, they needed way more slaves to cultivate and gather the cotton. The whole topic of owning slaves became a hugely divisive matter nationwide, and it ultimately played a significant role in starting the Civil War.