The Underground Railroad demonstrated to southerners, to slave holders, the extent to which slaves opposed slavery. To the extent to which some radical abolitionists, black and white, were willing to go to help slaves escape. And demonstrated the slow leaching of slavery from the border states which over time would leave them isolated in a slave-holding republic in the deep south. A slave-holding republic which slavery might be liquidated by constitutional means. They, therefore, struck a preemptive strike to create an independent confederacy. That independent confederacy cession led to a war and war, of course, led to emancipation and ironically the end of slavery itself.