AHC: A federal ban on slavery (equivalent to 13th amendment) by 1885, without a secession or suppres

Interesting. Thanks for the reply.  Well since that is an economically driven collapse of slavery leading to its legal end *only in the 20th century*, that amounts to Decades of Darkness *failing* my challenge.

Of course, that scenario is pessimistic by design.

-No repeal of the Missouri Compromise in the wake of Kansas - Nebraska Act 1854 though that would incense the Southern Slavestates and probably lead to Secession and a Civil War which You don't want.

-Cotton Boll weevil during 1820's which would prevent the spread of slavestates as southern states economy would be ruined to some extend if not shifted to other crops. Which possibly have the effect of all of US wanting the (former)slaves to emigrate just on a much larger scheme or exported to South America. Not really nice but might in a ban on slavery as an outcome.

Apparently, the US was contemplating purchasing more of Mexico or possibly even Cuba from Spain. If they came to fruition, you could have more slave states and maintain a numerical balance between slave and free states while avoiding the Kansas-Nebraska Act and by extension keeping the Missouri Compromise. Secession wouldn't be impossible but less likely in my view. By 1885, I wouldn't dismiss the Upper South moving to abolish slavery if they hadn't already since plantation culture wasn't as dominant as in the Deep South, and in general there was more industry. The Deep South is a different story. There might be rumors of secession in 1885 but without the Upper South, it becomes far less likely realistically speaking. That said, I can see the rest of the Union pressuring the Deep South to abolish slavery and if there is an agreement to abolish slavery over the course of 20-25 years beginning in 1885 then I can see an amendment being passed shortly thereafter banning slavery on a federal level and on a state level in the early 20th century.