Upon this land from 1620 - 1865 in southern states only and for 245 years did slavery exist. Only blacks were enslaved... not whites or Asians.
"The South" and those states comprising such convinced themselves that nullification of federal law by any state was a 'right' and as regards to outlawing slavery being a 'duty' to oppose such.
From it's founding until 1860 this nation debated the merits of 'slavery'. Newspapers were laden with opposing views sometimes covering pages.
Of ten million residents comprising "The South" only 500,000 'owned' slaves. Slaves numbered 3 million during the Civil War with but a few thousands escaping to the North during that conflict.
The Civil War cost 700,000 lives... 98% were white.