The North and the South had always been at odds. Since the creation of the country the two sides were always arguing with one another. Similar to now really except with less violence. Reports leading up to the Civil War involved violence between Congress men and I believe at least one shooting in the House. The two had vastly different cultures and were nearly their own separate countries at the point the Civil War began. The North was beginning to switch to an industrial nation while the South remained agricultural. So each had different economic pressures on them, which slavery was one of those pressures. Please do not insist that the North cared about slavery as a whole from some desire to save humanity. They did not fight the South because “friends” were being dragged away from slave hunters.
If you want an interesting and different look at the economics at the time, read “The Declining Significance of Race” by William Julius Wilson. He looks a great deal into industrialization and the effects of slavery on industrialization. With so many immigrant workers coming into the Northern cities looking for factory jobs, the slave became a problem to the “white” immigrant workers. A slave was free labor, no immigrant can compete with that wage. As a store owner why would you hire an Irishman to shine shoes when your black slave does so for free. There was a lot of infighting and violence at that time against slaves. Hence why slaves were not allowed in some areas of the North.
This is not to say there were not people fighting for the rights of slaves, but they were on both sides of the line. Southerners were fighting to free them just as Northerners were as well. The North simply had an economic reason to be done with slavery since it was steadily putting their people out of work and causing rampant poverty. A prime example of this is the mass exodus that happened after the Civil War. Whether this is irony or not, the North made a huge push on blacks to move back to the South and take up their jobs as agriculture workers. The sad humor is that these people then became share croppers and were essentially locked into contractual slavery with…wait for it…Northern business owners that were now buying the property.
People from the North like to use slavery as a moral high ground argument, but it simply falls short of the facts.