After the Revolution, the small number of slaves in the Northeast were freed. New York had more slaves than all the other Northern states combined had a very instructive experience with emancipation. About 3,000 self-liberating people left New York City with the British when they retreated to Canada. In 1785, the first attempt at emancipation became a bill that made all children born to slaves free. In one of those odd things that are so hard to explain, the potential freedom that .08 of the population was seen as a potential political threat.
In 1788 the slave trade was outlawed in New York. Special slave courts that had dealt out harsh punishments for even trivial offensives for 80 years was disbanded. The municipal ordinances that had perpetrated the custom of public flogging for slaves who were out after curfew needed.
In 1799 the Legislature passed "An Act for the Gradual Abolition of Slavery". In a complex set of rules, the act was intended to secure the return on investment for slaveholders. For example, male children were held in bondage until age 28. A flock of kidnappers & cheats taking slaves south for sale. One way to cheat the ban on slave sales was 99 year leases. Free blacks were not safe. Professional kidnapping gangs preyed on them, often with the help of corrupt authorities. The last legal vestige of slaveholding was not taken of the books until 1841.
Historian Edgar J. McManus has analyzed census data that charts a sharp drop in the growth rate of the black population after 1800.
"The conclusions inescapable, that the exodus was largely the work of kidnappers & illegal traders who dealt in human misery."
Edgar J. McManus, A History of Negro Slavery in New York p. 7.
<slavenorth.com> is an excellent source for information on the voluntary emancipation after the Revolution. My personal conclusion is that the moral rot inevitable with slaveholding means that slaveholders are slaveholders; the geographic location is merely a footnote.
How New York's emancipation of .08 of its population is any kind of indication of how South Carolina, which was staring an 80% slave population, might have managed voluntary emancipation defies my imagination.
I am assuming that in 100 years, that is by 1960, the dynamics of a slave labor based economics would have changed. I am unable to accurately predict what slavery in South Carolina would be like in 1960, just that in a 100 years some changes would occur. So possibly by 1960 South Carolina, like other slave labor states, just might be willing to agree to some form of peaceable abolition. I would fully understand if other forum members do not believe that the slave labor states might still not be willing to agree to some form of peaceable abolition in 1960.