Northern cities as early as 1780 were already practicing gradual emancipation. The southern cotton states were the only places that relied on slave labor (though the exploitation of the Chinese during the building of the railroads was in a lot of ways slave labor). Of course there were people who declared "The south will rise again" but as far as I am aware no real politicians (save KKK members) were pushing for the reiteration of slavery. I could be very wrong of course.