The three-fifths compromise has been disparaged by liberals because it is "offensive." Let's examine that and once again marvel at the mastery of the founding fathers.
For those who don't know, let me briefly explain that the "three-fifths compromise." In 1787, delegates to the Constitutional convention were arguing over representation and how to count people. Most slaves were in the South. Indeed, slavery was banned in the Northern territories (Ohio, Indiana, Illinois, Wisconsin, Michigan, Minnesota today).
Of course, population equals power in our government as the House of Representatives is apportioned based on population. The Northern delegates would be very outnumbered if the South counted everyone.
Even at that time, there was great unease about the practice of slavery. Many of the Founding Fathers were opposed to slavery, such as Patrick Henry. But there were big issues to uniting the states into one nation, and abolishing slavery was not the top of the list.
The Southern delegates wanted to count every slave as one person, which would have given them a large majority in the House of Representatives. The North argued not to count slaves at all since they could not vote. The compromise named the "three-fifths compromise" states that slaves were to be counted as 3/5ths of a person for purposes of representation and taxation.
There is a strange argument that the "three-fifths compromise" is racist. Considering that it was the Southern delegates, who owned slaves, who wanted to count their slaves as whole people should put that argument to rest. Clearly, they wanted them counted for purposes of power.
The North needed the South for many reasons. The biggest reason was food. The climate in the Southern states was and is much more conducive to producing crops than the Northern climate. The South felt that because their crops were so essential, they should have more say in the government. Making a compromise on the census kept the union together. But the South was more of a "states' rights" mindset, which was contrary at that time to the Northern idea of a centrist government. Arguments over the different philosophies led to secession of seven Southern states before Abraham Lincoln took office.
In the end, a Republican president, Abraham Lincoln, made the executive decision to free the slaves with the Emancipation Proclamation in 1863. And the 14th Amendment, adopted in 1868, made the Three-fifths compromise a thing of the past.