What are the most important issues I should discuss in an essay on the history of slaves in America from Columbus' time up until now?
The main period of slavery in the United States occurred between the early 17th century through the Civil War and the Emancipation Proclamation in 1863. Of course, some illegal slavery was still happening after the law changed: the film 12 Years a Slave documents the true story of a free-born African-American who was captured from the Northeast and sold into slavery on a Southern plantation.
Trying to capture the history of slavery in America in one general thesis statement is a challenge, as there are many complex issues to discuss. Would you be able to make your thesis address a more specific aspect of slavery? For example, one aspect of slavery that is important is the divide in opinion between the Union states and the Confederacy, and this disagreement became the basis for the Civil War.
Your main points could include issues such as farming: the growth of certain crops in the Confederate states relied heavily upon slave labor, such as cotton and tobacco, and to this day, those crops and their history are associated with the African slave trade in the United States. This was a large problem because the Southern states had an economy that relied upon slavery (or the use of slaves for inexpensive labor) to function. The North, however, had less need of slaves for economic prosperity, and it began to be seen an elitist and barbaric practice, to employ human beings as slaves, especially when it meant treacherous journeys by sea to steal people from their homelands in Africa and the Caribbean.
The Industrial Revolution occurred more widely in the Northeast because of the greater density of city population and the longer history of settlement, since the settlers of New England were the first to establish towns and later cities and these became the basis for the first Colonies. Therefore, the options for economic growth and industry were more diverse; whereas it was thought by many that the South's main industry was based in agriculture, which relied upon cheap labor, and many farms and plantations relied upon slaves to grow their businesses. This was part of the justification that led the Confederacy to fight to keep slavery going.
Other points to be made about slavery in America include the formation of African-American culture that occurred as a result of the arrival of so many Africans to North America: the effort to maintain tribal ways of religion, language, foodways and other cultural practices became very difficult for transplanted Africans, who were often expected to become Christians and learn English, and many slaves were punished if they tried to engage in their customs.
The history timeline included in the link below offers many important points about slavery, including different pieces of legislation related to slavery, and the main events of the Civil War.