At least they were in vocal defense of local rights when it suited their interests. A federal government responsible for finding, returning, and trying escaped slaves as enacted in the Compromise of 1850 and southern states were only too happy to invoke federal authority on behalf of The Cause.
Good point. The compromise of 1850 and the fugitive slave law it enacted often is overlooked in these discussions. While abolitionist sentiment existed in the North long before that, it was relatively limited and few people were overly concerned about slavery. The fugitive slave law was what really sparked a more widespread support for abolition.
It isn’t often discussed but it’s quite easy to ignore the plight of slaves when you never see any slaves, never really hear much about them and never really personally experience the result and consequences of slavery. There was no TV, internet or movies in the 19th century so few people were ever personally exposed to slavery and its actual effects. The fugitive slave law changes this. Escaped slaves were brought by abolitionists to cities like Boston and New York. People in those cities resented the southern owners who came to recapture their “property”. It is difficult for anyone with an ounce of compassion to see someone in such a desperate and hopeless situation escape from that situation and have to sit powerless while their own government allows them to be returned to that situation.
Besides the effect of the legitimate reclamation of escaped slaves another fact about this law is often ignored. The law set up a system where disputes over whether or not a slave was the legitimate property of a slave owner were to be decided by a federally appointed adjudicator. This adjudicator was to be paid per case, but his pay was based on his decision - he received double the pay when he decided in favor of the owner instead of the slave. Besides the fact that it would be very difficult for a free black person to provide evidence that he was not really a slave belonging to a plantation owner claiming him as escaped property, the financial incentive for the judge most often led to these cases being decided in favor of the owner. Essentially the fugitive slave law allowed de facto legal kidnapping and enslaving of free blacks living in the north.
Even still, abolition most certainly was not a majority position in the north, nor was it the motivation for fighting the war. The truth is that the North and South from the founding were really separate and distinct societies. The fact that they remained united as a single country had more to do with common external threats than anything else. The industrialization of the North led to an economically symbiotic relationship, with the South supplying raw materials for textile factories in the North. Those factory owners most certainly did not want to see abolition destroy their profitable system.
BTW OP, if the factory owners wanted land to grow cotton themselves, why would they not have just bought cheap land in undeveloped western states like Texas and Arkansas back in the 1840-1850 time frame? There would have been no need to go to war to get that land, and the cotton-growing lands further East were being depleted since cotton growing is very nutrient-draining on soil. The truth was that either secession or a complete overhaul of Southern society was inevitable. The South was surpassed by the North in every material way by 1860 -population, infrastructure, economic and industrial development etc. The only way secession could have worked is if the North was willing to allow it.
Don’t confuse results of the war with motivations for it. From the Northern perspective almost the sole motivation was preventing secession. Emancipation was a military and diplomatic measure (it ensured that Britain and France would not intervene for the CSA). Carpetbaggers infiltrating the Southern economy during Reconstruction likewise was a result of war, not a reason for it.