During the Revolutionary Era from 1765-1815, slavery existed in thirteen colonies. Maryland went from white servants to slaves. There was an agricultural economy that existed in the South that was dependent on the labor of slaves. Although slavery did not exist in the North exclusively; New York, Philadelphia, and New England were involved in the trade of slaves; so although the South was exclusively using slaves as an economic gain, the North also had financial benefits as a result of the existence of slavery. In the aftermath of the Revolution, slavery began to cease in the North. In Massachusetts they ruled slavery as not in concordance with the state. Other northern states like New York and New Jersey passed gradual laws saying "when a slave is born July 4th upon reaching the age of 21, they are free." Slavery was thus becoming sectional. The gradual laws were eventually let go cutting slavery more diligently. In the South, there was a discussion of slavery becoming a necessary evil. Manumission also came into process where owners had the ability to free slaves. Jefferson requested that as America expands, slavery not expand in the Southwest, but his request did not pass. The Northwest banned slavery, and in 1787 the Northwest Ordinance and the Constitution began to play a major role in the Constitutionality and legality of banning slavery.
In the Constitution, there are three parts that protect slavery. (1) Section 2: the 3/5 clause where a slave counts for 3/5 of a person. (2) International Slave trade: Africans are kidnapped and sold; Congress cannot ban this trade until 1808. (3) Demand Fugitive Slave clause (South): slaves who escape to the North are deemed by the Constitution to be returned to the South.
Under Federalism there was a National vs. State separation where specific powers were maintained for the National Congress and reserves some power for the states. Constitution had a clause giving the National