What central constitutional issue was settled by the civil war?

No, the civil war did not settle the ethical issue of slavery, however, indirectly it did settle the issue of whether or not slavery could would be allowed in the new territories. in the presidential election of 1860, lincoln led a campaign against the expansion of slavery into the new territories. as a result of lincoln winning the presidency, 7 states tried to leave the union of the united states and start their own union. this succession is the true reason for the civil war and by the north winning, the issue that was settled was that no state can leave the union.

February 1848 is when it was added. if that's what you were asking