The "Twenty Year Clause" of the Constitution banned the importation of slaves twenty years after the Constitution was implemented. The practice of slavery was allowed to continue, as well as slave trade between the states. The clause merely prohibited the addition of foreign slaves from Africa or other nations. The Founding Fathers expected the power of the South to be influential enough by 1808 to pass a bill to continue the trade. This did not occur, and the practice was steadily limited until internation trade was eliminated in 1808. However, due to the invention of the cotton gin, the demand for slaves rose exponentially within a short period of time. The smuggling of slaves was declared piracy in 1820. With a lack of imported slaves, cotton plantation owners had to find other ways to increase the slave population.
With no foreign way to increase the slave population, the American slave owners turned to forced breeding. Slaves were paired together, and forced to reproduce. Bred like animals, the "hardiest" slaves were paired together to produce strong offspring for future purchases. The American system of slavery is known as "chattel", meaning the complete ownership of a person, and their descendants. The breeding of slaves led to trade between the states. The high demand of slaves in the South was due to the change in agriculture, such as the invention of the cotton gin, and the increased profit that it promised. Much of internal trade took place from the Old South to the Deep South. There are few surviving records of the prices, trade routes, or export values, thus making it difficult to determine the exact economic results of the internal slave trade.