General Mung: Why would the CSA abolish slavery by 1900? What are the economic conditions that make it profitable to do so? What foreign nation has the influence to force the issue? And even if one did, say Britain, pushing for the abolition of slavery would remove cheap labor from the cotton fields, thereby raising the price of cotton being fed into Britain's mills.
OTL, there were 8.8 mln African-Americans in the US in 1900. Figuring 89% were in slavery in the south (the proportion in 1860), that implies 8 million slaves to be freed. What would be done with the slaves afterward? They were largely without education or an existing community of their own. No other nation in North America especially wanted them (at least not in those numbers), and shipping them all to Africa would be prohibitively expensive. The population of Canada at the time was about 7.2 million, split between Anglophone, Francophone and First nations. Do you really think there was going to be a majority black Dominion of Canada? Mexico had 14 million, but problems of their own.
Slaves were a major investment, the basis of both the Southern economy and the social structure. How would the resulting labor shortage be met?
How would the government offset the tremendous loss of wealth associated their emancipation? A young adult male laborer could expect to be worth in the range of $10K, in today's dollars. Taking millions of slaves out of the economy overnight would throw the economy of the south into instant recession, if not depression, with the CSA's GDP suddenly gutted.