“At the start of the American experiment, when the delegates from the individual states met in Philadelphia to rework the Articles of Confederation, there was a debate over power. It is not a debate that we often hear in our history classes, or read about in our textbooks, but this debate pitted the Northern States against the slave owning States of the South.
From the beginning, the South held the North hostage in the proceedings, refusing to budge unless the southern slaves were fully counted as part of a states population. This became an issue, because the South felt as though the populous North (which had dispensed of slavery by this time), would use their vast population (and the representation that such population would bring) to eliminate one of the key institutions of the Southern economy.
In the end, the delegates decided upon the 3/5ths compromise, which counted every slave as 3/5ths of a person.”..