One of the paradoxes of American history is the case of black slaves from Africa. All of them were from the Negroid race and the fact is that this trade was abetted by black slave traders who sold captured African  Negroes to white slave traders who transported them to America. 

At the time of the American War of Independence in 1776, the slave trade in black men and women from Africa was well established. The basic driving force for this trade was the economic factor. These blacks who were sturdy and strong were made to work on white owned cotton estates in the south and were a major factor in the economics of the region. the availability of cheap labor is the hall mark of an industry and the black negro filled that  void.

The first attempt to abolish slavery was made by Thomas Jefferson in 1784, when a proposal to abolish slavery was made in the Congress. Unfortunately the resolution was defeated by 1 vote. However a compromise was worked out and by the North West Ordinance of 1787, slavery was prohibited North West of the Ohio river. The reason for abolition of slavery in the North were again economic, as there were too many destitute  and poor whites, who needed a job and hence the black man could not be given guaranteed employment.

Another reason was the drive to go West in that great exodus to settle the "wild West", which was spearheaded by the residents of the Northern states. The Northern states had no slavery and only a form of color discrimination. American's  from the North and South,  thus had a split mentality as far as slavery was concerned.

There were some borderline states like Virginia, Maryland and Delaware. In these states there was a strong movement by Quaker and Methodist teachers and preachers who advocated that the owners free their slaves.This movement had an effect and the number of free blacks increased to 13.5%  of the population.

In the south the slave trade got entrenched. This was mainly because of the large cotton farms that mushroomed all over the south.  The requirement of cheap labor increased and from 1810 onward to 1860 upward of one million black slaves were  carried across the Atlantic ocean.

Another facet of the South was the setting up of the " human Farms" for breeding  of slaves.  These farms involved  indiscriminate sex  of black men with young African girls. Further these men  carried on inbreeding and and also slept with their own daughters with the black girls  and impregnated them. this had an effect and by 1860 the slave population had risen to 4 million and a flash point was reached. There is a documented case of a white man starting a "farm" with 2 black girls, which resulted in raising a family of 200 over a period of 30 years.

In 1861, the issue of slavery was at the top and Abraham Lincoln was keen to abolish it.  The South seceded from the Union and war broke out. Lincoln ordered the Union army into  battle and  after a savage  war from 1861-65, the South was defeated. Most of the big farm owners were reduced to penury. Perhaps it was Gods way of doing poetic justice.