The Welsh and Scots and a few Irish settled in the South, where I was born and bred. The North was settled largely by English (esp. Puritans), German-Swede-Norwegians, and a few more Irish. Thus the two very different cultures... rigid morals, rules, and work ethic of the North; relaxed Laissez-faire Libertarian approach in the South.

I once read a paper (lost in the mists of time now) that stated the Civil War between North and South was really just a continuation of ancient wars that occurred over the centuries back in Europe, but mostly in the British Isles, between Britons and the wild tribes of Scotland, Wales, and Ireland.