In high school I did learn about the tariffs that aided the industrial interests of the North and hurt the agricultural interests of the South.

I also learned that slavery was becoming uneconomic but that the invention of the cotton gin extended its economic life and King Cotton was born. Also slaves were counted as 3/5ths for purposes of determining how many Congressman a state got. As new states were to be introduced into the Union, the issue of slave free states was a major hot topic even though the North still allowed slavery in most states.

There were many issues separating the industrial North from the agrarian South.

Lincoln was losing the war until the Emancipation Proclamation. There were draft riots in New York as you could buy your way out of the draft. England had become anti-slavery decades earlier and this reduced their willingness to intervene.

Ultimately the industrial might of the north and the blockade of southern ports wore the south down.