As the new nation became settled, slavery became a part of it.  Many of the new settlements were large areas where slaves became an essential part of maintaining and developing these areas.  While Europeans came to the new world to establish their claim to new land, people of color were needed to maintain and tend these areas.  As economies of scale began to emerge in the new world with the discovery of crops such as tobacco, the profit generated helped to develop more lands and more slaves.  This began the process in the new world of increasing profit through slaves only to increase the number of slaves needed to generate more profit.  This continued well into the 1800s, culminating in the Civil War from 1861- 1865.  At the conclusion of the Civil War, a series of amendments were added to the Constitution, one of which, the 13th, abolished the formal institution of slavery.

Up until 1676, indentured servants were the primary source for labor in the New World.  Slavery, as noted, had begun almost as soon as the English colony of Virginia began to be settled, but slaves were a poor source for labor -- they were very expensive and they usually died within 7 years of arriving. Indentured servants were much cheaper; they too usually died within 7 years of arrival, but their sponsor was out much less money, as it was cheaper to pay for an indentured servant's passage across the Atlantic than it was to purchase a slave for life.

Tobacco became the primary export; its cultivation was labor intensive.

Slavery began in earnest after Bacon's Rebellion, in 1676.  The indentured and newly freed servants and small poor white farmers stormed various plantations and destroyed what they could in protest against the abusive practices of the large scale farmers.  The rebellion was put down, but afterwards racism was legally enshrined in a series of acts that were designed to give the poor white farmers more of a stake in the agrarian economy by excluding black farmers (up until this time, there were free black farmers who owned slaves!) Conditions had improved so that life expectancy was greater; slaves, rather than troublesome indentured servants, became the mainstay labor force for nearly the next 200 years; racism upheld the social and political structures in the South and has finally rapidly diminished in our own time.

American Slavery, American Freedom, 1975 HW Brands.

Slavery started in what is now the United States in 1619.  In that year, a load of slaves was dropped off in Jamestown, the first settlement in what is now the United States.  Slavery would continue to exist in the United States until the end of the Civil War, which was in 1865.

Slavery came to exist mainly because there was a serious need for labor in the South.  Paid workers did not want to work in the conditions that existed on Southern plantations so the owners of the plantations needed workers who weren't free.  They used white indentured servants for a while, but eventually turned more and more to black slaves.

Most people believe this change happened because it was easier to prevent black slaves from escaping and because black slaves would not feel that they had certain rights the way English people would, even if they were indentured.