As I stated at
https://groups.google.com/d/msg/soc.history.what-if/r17xzhZ4zmg/Pu_apwkipEoJ:
***
Let's go back to the question of whether slavery was declining before the
invention of the cotton gin or would have disappeared had it been invented
somewhat later. My answer is No to both questions.
It is a myth that slavery was dying out before the cotton gin. Too many
people assume that slavery equals the Southern plantation system equals
cotton. That was actually not true until *many* years after the invention
of the cotton gin. As late as 1800 only about 11 percent of all slaves
lived on cotton plantations. (By 1850, with greatly increased world demand
for cotton, that had risen to 64 percent.)
http://books.google.com/books?id=F-KIAOQxKigC&pg=PA30 Tobacco made a
considerable recovery after the Revolution, and spread to new regions in
South Carolina, Georgia, Kentucky, and Tennessee. Slaves were also used in
the production of rice, sugar (after Louisiana was annexed) and grains.
Of course, there *were* some areas of the South that were much better
suited for cotton than for any other crop--above all the black belt of
Alabama and the alluvial areas of Mississippi. But these areas were not
opened up to the plantation system until many years after the cotton gin. I
guess my problem with "no cotton gin" hypotheticals is this--I find it very
implausible that nobody would *ever* think of the cotton gin. And I don't
believe that a mere delay in its discovery would leave slavery so weakened
in the interim that Southerners would be willing to abandon it. "There were
in fact, almost as many Africans brought into the United States during the
30 years from 1780 to 1810 as during the previous 160 years." (Robert
Fogel, *Without Consent or Contract*, p. 32.) And these 30 years were a
period in which cotton was by no means dominant.
And southern congressmen in the early 1790's--well before the expansion of
the Cotton Kingdom--seemed as belligerent on the subject of slavery as
their counterparts of decades later. Consider the following remarks by
Congressman Jackson of Georgia in 1790 (before the cotton gin was even
invented) in response to some antislavery petitions:
"[T]he people of the Southern states will resist one tyranny as soon as
another. The other parts of the Continent may bear them down by force of
arms, but they will never suffer themselves to be divested of their
property without a struggle. The gentleman says, if he was a Federal
Judge, he does not know to what length he would go in emancipating these
people; but I would believe his judgment would be of short duration in
Georgia, perhaps even the existence of such a judge might be in danger."
http://books.google.com/books?id=DmkFAAAAQAAJ&pg=PA209
Likewise, Federalist Congressman William Smith of South Carolina on March
17, 1790 made a speech attacking federal interference which "developed
every argument for slavery as a positive good which Calhoun would bring
forward half a century later."
https://journals.ku.edu/index.php/amerstud/article/viewFile/2168/2127