David,

Good points, the Mormons are among the first that come to mind when thinking about religious movements that spawned from the northeast. Still, the image of Puritan New England weighed heavily during this time (and afterwards).

Much of the religious difference between churches in the South and churches in the North focused on varying denominations or movements within Christianity. Many notable abolitionists were very much Christian, and preached not only racial equality but gender equality. That was quite controversial not only in the South but other portions of the North, including the often conservative midwest. This aspect was not a dispute between Christians and secular humanists, but between Christians over the Bible and their view of God's plan.

I think this is a very interesting and complicated subject---far more complicated than Mr. King portrays.