Slavery did not originate in the British Colonies, although it later became dominant in the American southern plantation system.
In 1452 and 1455, Pope Nicolas V issued a series of papal bulls granting Portugal the right to enslave sub-Saharan Africans. He wrote, ". . . to invade, search out, capture, vanquish, and subdue all Saracens [black Gentiles] and pagans whatsoever …[and] to reduce their persons to perpetual slavery..."(3) Spanish monarchs Queen Ferdinand and King Isabel permitted Nicolas Ovando to import black slaves of African descent to Hispaniola (known today as the Dominican Republic and Haiti) in 1501. This is the first recorded instance of Europeans transporting capture black people for use as slaves in the New World.(4)
Through the 17th century, most Europeans and non-Europeans did not believe all men were equal or that liberty was a God-given right.
The number of Africans brought to Virginia in the first half of the 17th century was relatively small compared to the number of white English indentured servants. However, as it became harder to entice English laborers to Virginia, planters increasingly turned to using enslaved African workers. By 1650, there were about 300 enslaved persons in Virginia. By 1700, there were 6,000. By 1860, the slave population in the United States had expanded to almost 4,000,000 of which about 500,000 lived in Virginia.
Between 1667-1686 Virginia created a legal structure for holding black families in permanent slavery, and imported a huge quantity of slaves after 1700 to provide sufficient labour to grow tobacco. At the time of the first census in 1790, 20% of the residents in Virginia were slaves. [https://ofhistoryandkings.blogspot.com/2011/02/that-obnoxious-weed-colonial-tobacco.html]
The average price of a slave in 1850 was $400 (about $10,000 in 2021).(1) This varied depending "on the slave's age, sex, and the region in which they were sold. Young adult males had more value as they were stronger, could work harder in the fields, and could be expected to work at such a level for more years. Young adult women had value over and above their ability to work in the fields; they were able to have children who by law were also slaves of the owner of the mother. Old and infirm slaves had low, even 'negative,' prices because their maintenance costs were potentially higher than the value of their production. Similarly, young children had low prices because the 'cost' of raising them usually exceeded their annual production until they became teenagers."
In the New York Times on August 22, 1863, Page 4, it was reported:(2)
In the farther States of the Southern Confederacy we frequently see reports of negro sales, and we occasionally see boasts from rebel newspapers as to the high prices the slaves bring, notwithstanding the war and the collapse of Southern industry. We notice in the Savannah Republican of the 5th, a report of a negro sale in that city, at which, we are told, high prices prevailed, and at which two girls of 18 years of age were sold for about $2,500 apiece, two matured boys for about the same price, a man of 45 for $1,850, and at woman of 23, with her child of 5, for $3,950. Twenty-five hundred dollars, then, may be taken as the standard price of first-class slaves in the Confederacy; but when it is remembered that this is in Confederate money, which is worth less than one-twelfth its face in gold, it will be seen that the real price, by this standard, is only about $200. In Kentucky, on the other hand, though there is but little buying or selling of slave stock going on, we understand that negroes are still held at from seven to twelve hundred dollars apiece.
^(1) Measuring Slavery in 2016 Dollars