A Northern Wind

What if; the rebelion had not started in the south for slavery, but in the north as the Free States suecceded due to the federal governments willingness to not end slavery, but how could this have happened. Well in 1848, the Mexican armies would be destroyed and the US would take even more land form Mexico. In a effort to gain slave states above the line set in the Misouri Compromise, the Free States infuriated, rebelled.