I think that if the southern states hadn’t rebelled slavery might have lasted well into the 20th century. The slave states could have blocked any amendments to end slavery up to that point. The south had already started using slaves in the few factories that they had. I could see that expanding.
As horrible as the war was I find the idea of slavery existing in the United States into the 20th century much much worse. Slavery always made a mockery of our Declaration of Independence. And if you read the notes and letters of many of the founding fathers you can see that they knew this also and hoped that slavery would eventually end at some point.
“I think that if the southern states hadn’t rebelled slavery might have lasted well into the 20th century. “
Its economic rationale was already ending. Slavery ended in all of the Americas by the 1880s. In a lot of South America it had ended by the 1850s.
Plus railroads, mines, ships, manufacturing and any other cash-crops like sugar & tobacco.
In fact, there were no industrial era jobs slaves could not do.
Yes, DiogenesLamp & others insist that slavery was dying out even in 1860, and there's some small truth in that.
In border states like Delaware & Maryland where slavery was legal in 1860, the number of slaves was declining, while the number of freedmen increased.
The reasons were 1) high slave prices in the cotton-south, 2) ease of running away to Northern free-states & 3) large numbers of Northern anti-slavery immigrants to Southern slave-states.
However, as of 1860 there was no serious political discussion of abolition in either Delaware or Maryland, where slavery was unpopular, much less in Deep South states where it was considered "a way of life".
Indeed, Delaware had fewer than 2% slaves, but rejected the 13th amendment in 1865, did not ratify it until 1901!
So my point here is: even in states where slavery was arguably "dying out", politicians were unwilling to vote for abolition.
And there's more...
Posters like DiogenesLamp argue that had Woodrow Wilson been President of the Confederacy, he would have kept them out of the First World War even beyond 1917.
That would let the Germans win, which would have prevented the Second World war, the Holocaust & everything else bad in the 20th century, right?
No, not really, because the key point forgotten here is that 1917 Germans were already "proto-Nazis" -- they were already racial supremacists and except for actual gas chambers & ovens, practiced what the Nazis preached in the Second World War, including a form of slavery over conquered Eastern European countries.
So now imagine that slavery was victorious in the Civil War and again in the First World War, so when, exactly would it ever be rendered obsolete & ineffective?
Add to it the Confederacy's "Golden Circle" of conquered Caribbean & Central American countries, add in Islamic slavery, and Japanese racial superiority over other East Asians, and now look at the world's map -- what percent of the world is slave and what percent free?
Today we consider slavery pretty much of a dead-issue, because it was thoroughly defeated in wars, but what if it had not been defeated?
What if slavery had been victorious at every turn?
How would it ever be abolished, even to this day?