So, as I understand it, the invention of the cotton gin in 1793 was fairly directly responsible for calcifying slavery into the "peculiar institution" it ended up as shortly before the Civil War. Indeed, I've heard it said that without the cotton gin, slavery would have fizzled out in the US long before the Civil War-era.
So, what if? Let's say Eli Whitney hits his head right before he was supposed to invent the cotton gin, and for some reason no one else comes up with the idea until at least the mid-1800's (or whatever). What happens? Does slavery get phased out in the US around the time the British dropped it (early 1800's), or does it go on?