I agree Rob, once the agricultural industry began to be mechanized it would be cheaper to buy machines then to buy and maintain slaves, not to mention the morality aspects of it. Many in the South, including slave owners, found it repugnant to own another human being but the entire economy was built on cotton and rice, both very labor intensive (I have picked cotton in Arkansas, I knew then I would NEVER be a farm boy).

The first plantation to mechanize would have gained an economic advantage over the others. Then the liberals would have been yelling that Southerners turned the slaves loose without trying to take care of them.