I am certain that slavery in the United States would have been phased out naturally. Slavery was beneficial in the south because of low marginal productivity. The south was predominately an agricultural society, and it had not benefited from the mechanization it would benefit from in the decades directly after the American Civil War.
I have to agree with him on this. Slavery was dying out across the world, it would have been increasingly agitated against, it would have begun to get unprofitable (for the masters, that is - it was always unprofitable for the slaves). Many slave-owning Southerners felt it was a dying system and didn't even particularly like it - they simply didn't not like it enough to do much about it. Jonathan goes on:
"An important question to ask is whether or not the emancipation of the slaves during the civil war accelerated the post-war industrialization of the south. No longer benefiting from cheap labor, southern farmers had to radically increase production in order to remain profitable. This directly leads to another question: how long would it have taken to naturally rid the country of slavery?
There were important technological developments prior to the civil war: steel plows, seed drills, threshing machines, et cetera. The dramatic burst in agricultural productivity, however, occurred in the post-war (indeed, this increase in productivity directly after the war led to the industrial revolution of 1879-1906, since it allowed otherwise occupied labor to be restructured into more productive industries)."
I found all this very interesting, because I suppose I never really thought of the late twentieth century as a boom time for the South. Maybe you only learn this in Southern public schools, but I was always taught that the War retarded industrial development in the South, so the idea that the end of slavery encouraged industrialization seems unusual, albeit I suppose plausible, to me.
There are a couple of other developments that are worth considering here. First, the Jim Crow Laws were passed as the Reconstruction regimes began to subside during this same time period. In a lot of ways, blacks reverted back to a state of semi-enslavement. Sharecropping and credit extension from landlords cemented the reassertion of this semi-slavery, making labor cheaper and perhaps once again retarding the progress of industrialization.
By the early 1900s you had another force - the large-scale migration of blacks and others from the South to the North, known as the Great Migration. This would have increased the marginal productivity of labor and caused the South to substitute away from capital.
And finally, I hate to break it to my Austrian readers, but Southerners also often point to one source as the reason for the transition from being the "Cotton Belt" to the "Sun Belt": Franklin Delano Roosevelt. Between the New Deal, the military spending, and the military-industrial complex that continues to do a lot of work in the South, a lot of thanks goes to Southern Democrats and their allies in the White House.