Herewith, a cotton gin, near Clarksdale MS (where PAPER SON is largely set) in 1939. What does a cotton gin do? It gins cotton. No, seriously, it separates the seeds out from a boll of cotton. Why is it called a “gin?” I dunno. Can someone help?
But here’s the thing about the cotton gin: its creation invoked, in a big way, the Law of Unintended Consequences. Once it was invented (by a Northerner just solving a mechanical problem, or so he thought), human, meaning slave, labor was not needed for the time-consuming task of seed removal. That allowed cotton to become a profitable crop — more profitable than rice or anything else. In truth very little grown on Southern plantations would have been profitable without an endless supply of free, meaning slave, labor. (An interesting contradiction in terms, that, no?) But cotton was more marginal than most crops, until the gin. Then it became a good deal less marginal. The South rapidly moved to near-monoculture, and slavery became the foundation on which that rested. Any nascent anti-slavery movements were nipped in the boll, until finally the Civil War.
Always, always, follow the money.