Since the advantageousness (from a market POV) of cheap agricultural labor continues to the present day, I don’t see a point at which slavery would have ceased to be economically viable, but slave states where large-scale agriculture was and is inefficient might have eventually ‘flipped’ and abolished slavery. Delaware had few slaves when the Civil War began, Maryland and Missouri abolished slavery during the war. Eventually the ratio of free to slave states would have gotten over the 3/4 mark, probably around 1900, making the ratification of an antislavery amendment a near-term possibility, and the slave states would have either had to secede at that point, or negotiate a phased, compensated end to slavery.
It wasn’t all about economics, people. Ah, we live in such cynical times, don’t we? Our penchant for engaging in moral crusades, a product of a long tradition of exceptionalist self-image in America, has been so debased and misguided lately that we often overlook what a powerful force it has always been.
There is little mention above about the intensity of the moral crusade to abolish slavery which had come to crest at the time, in much of the South as well as the North. Certainly many thought slavery was still fine, even Biblically required, and many more didn’t much care, but it had already become a mainstream position, throughout the civilized world in fact, that it had to be ended because it was simply wrong.
Perhaps, without the Fugitive Slave Law and the Dred Scott decision, and with better political leadership than we had in the 1850’s (which wouldn’t have taken much), there might have been a softer ending to it instead of a brutal war and a century of continued repression, but abolitionism was certainly not going to fade away. The pressure wasn’t going to get any less intense. Slavery was going to be ended, and soon, one way or another, irrespective of economics. Most likely, ISTM, it would have been replaced with the sharecropper system, as actually did happen. But I don’t see any real possibility that the South could have kept it in place.
So, what specific scenario do you think most plausible? Are you saying that the southern states would shortly have abolished slavery due to nothing more that moral pressure? In historical reality, the south was willing to go to war just to ensure that slavery would spread. Obviously that is changed for the purposes of this hypothetical, but it seems a stretch to say that they would not have vigorously defended their ownership of slaves for at least decades to come. So, what do you mean by “soon” when you say that slavery was going to end soon one way or another?
The intensity of the pro-slavery sentiment in the South was essentially a *reaction * to being told they were morally wrong, don’t you think? Nobody likes to hear that, much less seriously consider the possibility that it’s true. But backlash is a transitory phenomenon.
That hardening of position, on both sides, made the war more likely, sure - but the topic was in play. Positions were being examined and discussed, even privately, that had not been examined and discussed in that way in the past. That process, when applied to other matters of social change that have been impelled by moral crusades rather than pure economics, has usually led to the crusade winning, after some period. We saw it in the establishment of women’s voting rights, a process that was peaceful enough in the US to be sure, but involved bloody rioting in Britain. We saw it in the end of Jim Crow (and the final end of the Civil War) in the Sixties, when the backlash from segregationists was followed by their acceptance. We’re seeing it today, piecemeal, in the backlash against anti-gay discrimination being followed by reconsideration and acceptance as well. What was all that different about the moral crusade against slavery?
Just how the end of slavery could have happened, not exactly peacefully but without a war, is certainly speculative given that the backlash didn’t have time to dissipate. But, as I said, the fact that it was relatively easily replaced with the sharecropper system after the war suggests that that could have happened without a war.
But the acceptance of integration by former segregationists only happened after the federal government stepped in and forced it upon them. What they accepted was already a fait accompli. Is it so clear that it could have happened without this sort of top-down enforcement?
There are two issues here, social (or economic) and legal. On the latter, it’s important to recall that under the conception of federalism obtaining at the time, no one (including Lincoln, who was quite explicit on the subject) thought the federal government had the power to outlaw slavery in the states in which it was permitted. Only the great expansion of federal power during the Depression would have permitted that. And passing a constitutional amendment with the South not in rebellion would have been impossible. OTOH, repeal of the Fugitive Slave Law (assuming the South lost its veto position in the Senate) would have made slavery less tenable. But I hesitate to believe it would have brought the Peculiar Institution down.