The English did not immediately enslave the Native Americans when they arrived at Jamestown, nor did they bring slaves from Africa in the first years. Slavery was a familiar institution to the English, but in the 1600's nearly all labor in England consisted of free workers.
For years a Dutch ship was credited with bringing the first slaves to Virginia in 1619. Latest scholarship indicates that two English pirate ships intercepted a Portuguese ship in the Gulf of Mexico, then transported slaves to Jamestown. The Portuguese ship had acquired a cargo of slaves in Angola, and was planning to sell them to Spanish in Mexico.
The Portuguese had been importing slaves from Africa for over a century, and the Spanish had enslaved the Indians in Central and South America to work the mines and to grow crops. John Smith had been a slave himself, after being captured by the Turks. He claimed that a beautiful woman helped him escape, a story that parallels his tale of Pocahontas.2
The Virginia colony lacked a legal framework for slavery until 40 years after that date, and the great increase in the slave population did not start until 1700. Tobacco was a labor-intensive crop. Each slave or indentured servant working on a tobacco plantation may have processed 10,000 plants a year. That would require bending over 10,000 times to plant seeds, 10,000 times to dig seedlings from the early planting bed, 10,000 times to plant seedlings in a field...
As plantation agriculture spread up the Potomac River, the demand for field workers exceeded the supply of people in the colonies and England willing to do such work. The economic solution was to obtain laborers from another source - slaves from Africa, imported through the Caribbean islands as well as directly from that continent. In the 1660's, the demand for labor in Virginia exceeded the supply of indentured servants from England after the end of the civil war there.
slavery was developed in Virginia so planters could acquire a cheap labor force to grow tobacco
Source: Library of Congress, Tyler, His Family and His Allegiance to the South
The Virginia colony revised its laws in that decade to establish that blacks could be kept in slavery permanently, generation after generation. An influx of slaves was spurred at the same time by a drop in the value of sugar grown on Caribbean islands, causing the planters there to sell their "property" to the tobacco farmers in Virginia.3
There is a continuing debate regarding whether racism against blacks preceded the adoption of a legal system upporting lifetime slavery in Virginia, or whether the practice of slavery triggered the colonists' racist attitudes. Blacks were not automatically slaves in the early colonial days. Some held property, married, and raised families outside the institution of slavery.
In the 1660's, however, the government of the colony (not the officials in London...) established the legal framework for perpetual servitude based on color. "Every year between 1667 and 1672 the General assembly enacted legislation which increasingly defined a Virginian's status by skin color. Similar laws followed in 1680, 1682, and 1686. By the final decade of the seventeenth century, those characteristics most associated with the plantation society of the eighteenth century were already evident."4
The slave trade lasted almost 200 years, until the importation of slaves was officially prohibited in 1808 by Article I, Section 9 of the US Constitution:
Most Virginia slaves were apparently imported from the Caribbean islands, rather than shipped directly Africa. According to the acting governor in Virginia in 1680, "what negoes were brought to Virginia were imported generally from Barbados for it was very rare to have a negro ship come to this Country directly from Africa." 5
Virginia was a center of the slave trade after the import of slaves was banned in 1808, and shipped Virginia-born slaves to fast-growing states along the Gulf Coast
Source: Library of Congress, Slave Auction