Q--

"If" the war had been avoided.

1) "If" is a huge "if".   As you know, southerners had already for decades been opposing restrictions on slavery--including spreading it westward.

2)   "Plantation managers would soon have realized..."--ah but economics was not the only factor in play here--the whole social system depended on slavery--and the southern elites were showing no signs of wanting to relinquish their position. Recall that even enlightened men such as Jefferson were unwilling to give up their standard of living, made possible by slavery. Many poor whites also saw slavery as the their ticket up in society.

If anybody has information on the abolitionist movement in the South mentioned by Bobert, I'd like to hear more.