When the first families, immigrants who engaged with agricultural trade, arrived in Virginia, they spread along the river to grow tobacco. This plant soon dominated Chesapeake’s agriculture and the demand for the product became high in Europe. It became the cash crop for the southern colonies. Tobacco was cultivated on fertile soil next to the rivers so that it could be transported. The planters were in control of both exports and imports, allowing the merchant class to develop. Urbanization slowly came underway and people migrated from England to Chesapeake as workers.

http://usslave.blogspot.dk/2008/12/tobacco-slavery.html 

Later on, a decline in the tobacco economy in the south forced a shift to the short staple, cotton. With the textile industry exploding in Britain, there was a huge demand for cotton in the Deep South. Thanks to Eli Whitney’s cotton gin invention, there was an easier and more efficient way to separate the seeds from the cotton fiber. The only thing left to fuel the economy was the powerful driving force of slavery. The textile industry expanded and industrialization followed with the number of cotton mills increasing. 

http://www.davidmcelroy.org/?p=13064

In both situations with cotton and tobacco, plantations began to increase, causing a demand for slaves and ultimately resulting in the forced migration of the Middle Passage. Thus, the triangular trade was developed as tobacco and cotton were shipped from the Americas to England, manufactured goods were then given to Africa, and slaves from Africa were moved to the Americas. However, the forms of slavery quite differed from one another. In the Chesapeake region, planters organized slaves into gangs to work the tobacco crop. For cotton however, the slaves lived on large plantations with many other black workers and were not in much contact with their masters. Both types of slaves still endured terrible working conditions to produce these highly demanded crops which in turn helped lead to the foundation of the United States.

http://kindreda.edublogs.org/files/2010/09/blog6.jpg

check it out!

http://www.bbc.co.uk/worldservice/africa/features/storyofafrica/9chapter5.shtml