Because more slaves were needed, there was a slave (and cotton) explosion in the USA. By 1820, slavery had spiked because of the plantation owners owning more slaves and land, and the widespread use of Eli's cotton gin.
Cotton production. credit aiimpacts.org accessed 2024. .
Slave exports. credit statistica.com. accessed 2023
Contrary to what actually happened, Eli said he thought that the cotton gin would actually stop slavery, stating that since they needed fewer slaves to pick the cotton apart, they wouldn't need as many of them to produce cotton at the same level. This was true, but, by 1800 cotton was king and became a cash crop. This eventually led to sparking the Civil War with the South wanting to have the cash crop of cotton, but the North not believing in slaves and farming, instead believing they should be compensated for their work. These were the main effects of the invention of the cotton gin.