Really, what can one say about slavery? It has existed since the beginning of recorded history and the United States can claim no innocence from it. A set of colonies that would become the United States accepted the practice fairly early and continued it for something like 250 years.
The American brand of slavery (also known as Dutch-American slavery) differed from other forms of slavery in certain subtle respects, but a complete comparison of the various forms of "ancient" and "modern" slavery are well beyond this writing.
Nearly empty ships would make the first leg of their voyage from England towards the African coast. There the crew would load their cargo of human beings, purchased and otherwise acquired in a variety of ways. They would be chained below decks, laid side by side, row upon row upon row. In the end, the cargo would hold as many as 600.
The slave ships then began the dreaded middle passage across the Atlantic. Many of the Africans below would die as they starved or succumbed to various wounds and disease. Routinely, at least a third of the inhabitants would die. If a communicable disease began to spread among the slaves-to-be, those infected would be thrown overboard to face the relative mercy of the ocean.
Arriving in the New World, the survivors were traded for sugar, molasses and other supplies, which were then carried to England, where the cycle would repeat. The survivors found themselves spread across the New World, forced into slavery. They were immigrants without a choice; citizens with nothing but their hoarded dignity; taxed without representation; slaves.
Yet, they were always survivors. Wherever they ended up, they multiplied, revolted, created thriving cultures, advanced and revolutized. They survived. And their descendants are still here, surviving... and thriving. We are they.