And my in-depth study of American economic history will tell me that once, what you identify as the primary cause of Southern backwardness, slavery, was gone the South became a powerhouse of industry, banking and trade with a lot of innovation? The same that happened in Jamaica and Haiti when slavery was gone?
Factories used forced labor before, during and after the Industrial Revolution but why modern industry preferred a free workforce it's another debate. The first textile machines were so effective at labor saving that the cost of labor for machine workers was not in a real competition with the huge cost of pre-industrial workers free or slave. The high productivity resulted from technology allowed the West to flourish for the last two centuries despite a higher cost of labor.
So, slavery did not prevent SOME innovation but it may have been MORE innovation if there was no slavery, a statement that obviously can not be proven.
Regarding one of your earlier questions I believe that the Classical Athenian democracy that ruthlessly exploited large numbers of slaves in the silver mines in Laurium was the most innovative society of it's time.