BS. Freedom vs Slavery was the 1860 conflict.
If that were the case, the Emancipation Proclamation would have freed all slaves, not just those in the 'South'. In fact, the 'North' had slaves before the 'South', and kept them after those in the 'South' were free.
It is not surprising, therefore, that the 'underground railroad' did not end until it reached Canada. There was no freedom for slaves in the 'North'.
It remains fashionable to paint the US, and especially the south, as the prototypical bastion of slavery. Being so passionately fashionable wrongly convinces the rest of the world the we are the worst slavers of all time. In fact, quite the opposite is true.