Originally Posted by
Odysseus
It was a lot rarer in the north, especially after the Missouri Compromise. Besides, the industrialization of the north required massive urban populations that could work in factories, and slavery was not conducive to skilled labor. This was satisfied by voluntary immigration from Europe, especially Ireland. This is one of the major reasons that there was a Civil War, although it's not covered very extensively at the undergraduate level, much less K-12.
In a nutshell, the northern economy was heavily industrialized and depended on raw materials from domestic sources to feed the mills. These came from the south. Britain, which was also heavily industrialized, had a head start and had more capital to spend, so they were able to outbid the north for southern crops, specifically cotton. Since the northern industrial base attracted more immigration, this led to a population increase that meant more representation in the House of Representatives, where northern interests were more heavily weighted. That's why the Senate was where all of the compromises happened. If you look back on the history of tariffs and other trade restrictions, you see the legislation that came out of the house was almost always hostile to southern interests, while the senate always mitigated the damage. This was the underlying economic schism between the north and south. The underlying social schism was the urban culture of the north, which saw southerners as illiterate yokels or elitist plantation barons, vs. the agrarian culture of the south, which saw northerners as crude, corrupt city dwellers who were constantly cheating southerners of their rightful due. Throw in the emotional arguments regarding slavery and you have a vicious divide over issues which could no longer be settled amicably. The election of Lincoln in a fourway race guaranteed that his administration would be seen as both illegitimate and radical by his opponents.
Now, want to see something really scary? Compare the social split between north and south with the social split between liberals and conservatives. Abortion is the emotional argument that divides the two camps (as are gay marriage, gun control and immigration), while entitlement policy (welfare, social security, health care, trade protectionism) is the economic schism. See you in the trenches...