The history of the transatlantic slave trade has its beginnings in European colonialism and owes it's abolition to the Age of Enlightenment and American Liberty. There is plenty of credit and blame to go around when discussing the struggle of slavery and the complexities of abolishing it, but I think if you look at the forces that moved the world away from slavery you will find the first stirrings of this movement in the same forces that moved American patriots to break with their motherland and proclaim that ALL men are created equal.
Two hundred years after the African slave trade began there was a stirring in Europe and it's colonies, a new way of looking at man's relationship to God and thus man's relationship to society and other men had developed out of the Reformation and turned into a full blown Enlightenment. The central doctrines of the Enlightenment philosophers were individual liberty and religious tolerance, in opposition to an absolute monarchy and the fixed dogmas of the Roman Catholic Church. Unlike the more modern revolutions of thought that have come out of communism and humanism, the Age of Enlightenment began among 17th century Christians. It was Christian reformers who introduced the world to the ideas of political equality and individual liberty that paved the way for the political revolutions of the 18th and 19th centuries and threw off the yoke of European colonialism.
As a natural expression of Enlightenment ideas, Christians began to condemn the practice of slavery as an abomination in the sight of God. In the beginning abolitionist were a small but passionate group of believers. The abolition movement received most of it's early traction by the pious in the American Colonies who saw first hand the human horror of slavery. Quakers in Pennsylvania were some of the earliest activist against slavery in the American colonies.
Even while these passionate abolitionists spoke out against slavery and colonization, as many as 6 million Africans were transported to the Americas as slaves. At least a third of them were transported in British ships to the British colonies of North America, but what few people realize is that the numbers of enslaved Africans in North America made up less than 5% of the twelve million enslaved people brought from Africa to the Americas during the African slave trade. Still the impact that these enslaved Americans would have on the abolition of slavery in the western world was profound.
The British colonies of North America were unique in how the colonialist reacted to living among the slaves imported by the British crown. Many of the colonies would not long tolerate slavery among them and others hold onto it until their land was soaked in their blood. While the abolitionist movement in England and her American colonies would grow up together, the ideas that American patriots consumed from Enlightenment philosophers and the experience of living free in the wilds of the New World set America on a path that would have a profound affect on the political landscape at home and in the United Kingdom. The workings of the Enlightenment in Europe and in the British American colonies would birth a new nation conceived in liberty and dedicated to the proposition that all men are created equal; and the movement to end the international slave trade would become a shared work for both motherland and it's revolutionary progeny.
1688 - Abolition of the African slave trade may have had it's conception in Quaker Pennsylvania. Influential Quakers in the Society of Friends wrote a two-page condemnation of slavery, it has been held as the earliest political document laying forth a forceful argument against slavery. The principles laid forth would be sited as a foundation for the abolition of slavery among the Society of Friends in 1776.
1733 - Believe it or not the first colony to ban slavery was in the south. Slavery was banned at the establishment of the Georgia Colony under the leadership of James Edward Oglethorpe, the founder of the colony of Georgia and a member of the British Parliament. Oglethorpe's ban of slavery caused serious strife between Georgia and it's neighbor South Carolina which led to the first debates over slavery in the British Parliament where Oglethorpe became the first to articulate the Enlightenment case against slavery in 1740 and 1742. Though Georgia would eventually succumb to the pressures of slaves states surrounding it, this first ban of slavery contributed to the First Great Awakening of the 1730's and 1740's in the American colonies; a Christian religious revival that was part of the wider Age of Enlightenment. Rationalist thinkers and Christian Evangelicals, who were also influential in the move for Independence that led to the American Revolution, criticized slavery for violating human rights. Anti-Slavery ideas were well developed and cultivated among the patriot north in pre-revolutionary America, however, an steep ideological divide developed between the northern colonies the southern colonies. While northerners used the bible to teach against slavery the southerners used it to defend the "tradition" of slavery.
1772 - In the United Kingdom, Lord Mansfield's judgement in the Somersett Case would eventually lead to the emancipation of slaves in England and is viewed by many as the launch of the political movement to abolish slavery in the United Kingdom. Others place the beginning of the anti-slavery movement about ten years later when British public opinion began to turn against slavery.
1775 - Thomas Paine's article "African Slavery in America" is considered to be the first American patriot to publish an essay advocating for the abolishing slavery, though the personal writings and correspondence of many of Americas founding fathers reveal that they were in favor of abolishing slavery.
1775 - In the English colonies of North America, "The Society for the Relief of Free Negros Unlawfully Held in Bondage" is formed in Philadelphia Pennsylvania, it would be renamed after the revolution and become the "Pennsylvania Abolition Society." Benjamin Franklin would be its President. It would be one of two primary organizations that would advocate for abolition, the other being the New York Manumission Society led by John Jay and later Alexander Hamilton, two of the authors of the Federalist Papers.
1776 - In the newly independent states some southern slaveholders began freeing their slaves as early as 1776. Slaveholders in the upper south freed slaves in such numbers that the percentages of free Negroes increased from 1% in 1776 to 10% in just ten years, most of the increase was in Virginia, Maryland, and Delaware. By 1810 tree-quarters of blacks in Delaware were free. Robert Carter III freed 450 people in 1791, more than any single American before or after. However, southern states did not want free blacks and prohibited free blacks from entering their states and required that newly freed slaves leave the state within thirty days. They also banned abolitionist and their writings from entering their states.
1777 - Beginning with Vermont, most of the northern states abolished slavery even before the drafting of the U.S. Constitution and the birth of the United States of America. Emancipation was gradual but it was an value woven deeply into the fabric of the new nation.
1779 - Massachusetts ratified their state constitution which declared that all men are equal. This led to subsequent suits that abolished slavery in Massachusetts via the courts. In the south similar declarations of rights, such as the Virginia Declaration of Rights written by Thomas Jefferson, were interpreted by southern courts as not applicable to Africans. The Massachusetts state constitution and the Virginia Declaration of Rights are seen by Constitutional scholars as some of the most important documents that influenced the writing of the United States Constitution.
1780 - Pennsylvania passed legislation to abolish slavery over the next two decades. A progressive emancipation that was very successful and led the way in plans for the progressive abolition of slavery within the United States and the United Kingdom.
1780 - Immediately following the American Revolution, northern states, beginning with Pennsylvania in 1780, began abolishing slavery, sometimes by gradual means.
1787 - In the United Kingdom, William Wilberforce begins his career and crusade to end the slave trade.
1788 - The U.S. Constitution is ratified and the United States becomes a nation. Article 1, Section 9, Clause 1 of the Constitution was added in order to appease the southern states and prohibited the Federal Government from abolishing the slave trade until 1808. Even from this time it was assumed by all at the Constitutional Convention that the slave trade would be outlawed in 1808, even the southern states understood that this was the direction the country would take which is why they insisted on the article which would give them twenty years. Thomas Jefferson, a southerner and slave holder himself has been advocating for the abolition of slavery since the 1770's. During the next twenty years public opinion against slavery would only grow in the United States and England. The United States would use the interstate commerce powers to regulate and restrict the international slave trade and the expansion of slavery within the United States.
1787 - The Northern Ordinance under the Articles of Confederation ended the slave trade northwest of the Ohio River. The same year delegates to the Constitutional Convention in Philadelphia debated slavery and the possibility of outright prohibition, however, it became clear that it was impossible to accomplish both the unification of the states and the abolition of slavery because the southern states would never agree. The only prohibition that could be agreed upon was on the import of slaves, but this abolition of the slave trade would be postponed by twenty years as a compromise to appease the southern states. What is little known is that by 1808 all the southern states except South Carolina had passed laws abolishing or severely limiting the international buying and selling of slaves and that it was without controversy that the 1808 act was passed.
1788 - In the United Kingdom the British Parliament places the first limitations on the slave trade. The United States would pass it's first regulations and restrictions on slavery in 1794.
1806 - Thomas Jefferson, the President of the United States, calls on congress to end the international slave trade in the United States as soon as constitutionally able.
1807 - In January of 1707, both the U.S. Congress and the British Parliament introduce legislation to abolish the slave trade. In February both legislative bodies passed their respective legislations', and on March 2, 1807 Thomas Jefferson signed the Act that would make the slave trade in the United States illegal on the soonest date constitutionally feasible, January 1st, 1808. The British law receives Royal Assent on March 25th, 1807. The British law imposed fines on slave traders but it did not deter the international slave trade. Between 1808 and 1860 the Royal Navy patrolled the Atlantic to suppress the slave trade but did not stop it entirely. A clandestine slave trade continued in the British empire until the 1870s. In that time the Royal Navy captured 1,600 slave ships and freed 150,000 Africans. By the late 18th century, the British empire who were responsible for planting slavery in North America became the world's most important force abolishing the transcontinental slave trade.
1820 - In the United States, the Missouri Compromise was a victory for pro-slavery Democrats would agree to admit the Republican free state of Maine to enter the union if Missouri was also allowed to enter the union as a slave state. The anti-slavery factions exacted a compromise for what was a very unpalatable expansion of slavery into the west by adding a provision which would exclude slavery from all remaining lands of the Louisiana purchase north of the 36 parallel. Democrats in 1854 would repeal the compromise with the Kansas-Nebraska Act, making it feasible for slavery to expand if mid-western settlers voted for it. They argued that prior to the Louisiana Purchase of 1803, Spain and France had sanctioned slavery in the region, Louisiana and Missouri were already slave states and therefore it was only fair that the rest of the territory should be able to choose for themselves. Following the war of 1812 the Missouri territory had rapid settlement by slave-holding planters and after the Nebraska-Kansas Act slaveholders poured into Kansas to try and effect the outcome of slavery there. This would ultimately lead to the Kansas War and increased tensions over slavery that would lead to the Civil War.
1823 - The Anti-Slavery Society was founded in London and among its founding members was William Wilberforce.
1833 - The British Parliament abolishes slavery in the United Kingdom but it carved out exceptions for the "territories in the possession of the East India Company" and the islands of Saint Helena and Ceylon, which remained in place until 1843. The loss of life and property in the Jamacian slave revolt of 1831 greatly contributed to the Slavery Abolition Act. The House of Commons had its first reading of the act on July 26th just three days before William Wilberforce died, and received Royal Assent August 28th. The Act went into effect a year later. The emancipation of slaves was gradual. The immediate effect of the act was the complete abolition of all slaves under six years old. For all other slaves there servitude was abolished in two stages. The act provided to slave owners payment for the loss of the slave as a business asset. The payments amounted to 40% of the treasuries annual income or 5% of the British GDP in 1833. The British took out a loan to finance it and the loan was not paid back till 2015. The payments went to hundreds of British families many of whom were of high social standing.
1839 - In the United Kingdom the Indian Slavery Act extended the abolition of slavery to the East India Company and the islands of Saint Helena and Ceylon, benefiting 8-10 million slaves. The same year the Anti-Slavery Society branched out and became the "British and Foreign Anti-Slavery Society," which worked to outlaw slavery world wide. It is held as the world's oldest human rights organization.
1840 -1965: Meanwhile the United States of America struggled to abolish slavery at home. Unlike Great Britain who had the advantage of their activities in the slave trade being oceans away from their homeland -- out of sight - out of mind --- slavery had been planted in North America and woven into the social and economic fabric of the society long before the birth of a new nation. The fledgling United States of America was challenged to live with slavery and then tasked with the complexities of emancipating the slaves without causing the dissolution of their fragile new union. The direction was set early. America was on a crash course with slavery and one way or the other it would be abolished. The abolitionist movement grew-up in the northern states long before Britain acted to abolish slavery in the United Kingdom, but the back lash from the south would result in a deadly divide between the north and south that would prevent the total abolition of slavery in the United States until 1865 as a result of the American Civil War. While the British had the luxury of paying off families at home for their divested "business interests abroad" and therefore ending the involvement in the evils of slavery, America would pay a much higher cost for the abolition of slavery, they would pay for it with blood.
Clearly it's a misreading of history to say that slavery was the original sin of the United States of America and that the United Kingdom lead out in the abolition of slavery. The harder task in ending slavery fell to the former colonies of Great Britain, the United States of America, and as a nation they rose to that challenge and laid down their lives on the proposition that all men are created equal.