But the real reasons were more racist, northerners wanted to keep the new territories lily white and free from the untermensch black encroachment. Everyone knew slavery was dying and they wanted to per-empt a black invasion.
IOW, blacks were undermenschen and therefore legitimate prey for the ubermenschen white race. Most northerners, while unwilling to recognize blacks as social and political equals, at least recognized they had the inalienable rights outlined in the DoI, to life, liberty and the pursuit of happiness. Southerners denied them even those limited rights.
If the North had really had as its prime objective keeping the existing territories melanin-free, they could easily have struck a grand bargain with the South that would have accomplished it.
The USA becomes a conquering imperialist nation. The North gets Canada, the existing territories and the rest of North America for its black-free zone; and the South uses the military potential of the united country to expand into Mexico, the Caribbean and Central America, perhaps eventually South America, creating a great tropical slave empire. Numerous southerners were in favor of such a bargain, notably including Jefferson Davis.
This would have required a drastic change in American culture and at least one war with the British Empire, which unfortunately had a much more powerful fleet. But it doesn't seem likely such a war could have been more devastating than the one we got.
CVA, I'd like to lay out my biggest issue with your posts. For your claims to be true, every public figure of the 1850s and 60s, North and South, would have to be an egregious liar.
Men of both sections spoke at extreme length on their beliefs and goals, yet for your meme to be accurate, everything they said would have to be cover for their true objectives.
Northerners, by 1860, were largely united in opposition to slavery, varying from a desire to keep it from spreading into new areas to full-blown abolition. Over and over they spoke, wrote and campaigned for these positions. Yet you would make this only a cover for their racist desire to keep the west for white people. Which is kind of silly, since at the time nobody needed a "cover" for racism, which was the popular conventional wisdom in both sections.
OTOH, southerners insisted that slavery be allowed to expand into the territories, and hopefully into new territory acquired y purchase or war, with some for the notion that the Constitution protected slave "property" even in a (northern) State that prohibited the institution. But, according to you, when they said so, over and over again, they really believed that slavery was on its last legs and they would soon be forced to abolish it for economic reasons. IOW, their constant claims of the bright future of slavery were conscious lies.
See Senator Hammond's famous 1858 King Cotton speech. (BTW, he was an "interesting" guy. Bisexual and incestuously intimate with four teenage nieces.) Couple quotes from him:
"I firmly believe that American slavery is not only not a sin, but especially commanded by God through Moses, and approved by Christ through his apostles."
"I endorse without reserve the much abused sentiment of Governor McDuffie, that 'slavery is the corner-stone of our republican edifice;' while I repudiate, as ridiculously absurd, that much lauded but nowhere accredited dogma of Mr. Jefferson that 'all men are born equal.'"
Why do you believe all the leaders of the country, North and South, were such horrible liars for an entire decade?