Back when I was in school it was taught that the cotton gin was the beginning of the plantation system growing to the point of its power being the main reason slavery remained. Of course there were plantations before but they were not primarily cotton based. My question is this: what if ELi Whitney had not invented the gin- would someone else have done it only later, and how much difference would it have made?
WIthout the gin, cotton does not become the primary southern crop; and the rationale for large plantations and lots of slaves is reduced greatly.
The impact on the south and the whole slavery issue= how much would have changed?
This is one I've thought about some-not like AHs of the early 20th century, but it's interesting nonetheless. Let's say lightning hits Whitney's workshop in the early 1790s, starting a fire that burns it to the ground, destroying his models, notes, etc. (Don't forget that by this time Whitney was already established as a proto-mechanical/industrial engineer, developing the concept of interchangeable parts.) Faced with starting over, and faced with the knowledge that the budding mills of New England gace challenges in efficiencey and capacity, Whitney opts for the latter, and becomes one of the great progenitors of the American industrial revolution.
Meanwhile, various other part-time mechanics and inventors are working to solve the problem of de-seeding cotton mechanically. Since prior work on the problem was essentially lost in the Whitney workshop fire, it's back to square one. Let's say a young mechanic in South Carolina comes up with something workable-but it probably won't be until well into the first decade of the 1800s--roughly the end of Jefferson's second term in office. That's maybe fifteen years later than in OTL: plenty of time for more diversified agriculture to develop through the south, as well as some of the extractive industries, like logging and sawmill operations concerning the pine forests.
I'm guessing that instead of plantations requiring large amounts of slave labor, what may evolve would be a series of small towns devoted to logging, sawmilling, and naval stores (that is, the extraction of turpentine and similar products from pine). Initially, these would be one-owner towns not unlike plantations, but the relative rural isolation (slaves as lumberjacks/sawmill hands/rough carpenters) makes for an unusually high percentage of runaways. And recapturing slaves becomes inefficient and increasingly difficult, since the rough-and-ready proto-industrialization gives these slaves--ironically!--skills that would allow them to fit in, however peripherally, to the more industrialized society of the north.
The owners in these southern company towns are then faced with Hobson's choice: fold for lack of manpower, or manumit the slaves and hire them on at wages that will keep them there.
I'm guessing that if things unfolded more or less along these lines, by the 1830s, slavery is all but dead save for a few really large traditional agricultural plantations in Mississippi, Louisiana, and perhaps Alabama and Georgia--enough so that while there are cries of protest, manumission legislation passes at the federal level not long after the British Empire abolishes slavery. In a further irony, by then, the development of the steam engine is such that large scale cotton gin operations are feasible and economically practical--but now what feeds those are cooperatives of smaller farmers, not a few of which are former slaves.
To take the irony further, apart from the pine forest-based company towns, the south in this timeline has become more Jeffersonian, if you will, than in OTL. I don't see a civil war as in OTL happening.