The issue of slavey was a major cause for debate at the Constitutional Convention. The convention was held because the previous attempt to organize American government, the Articles of Confederation, needed serious revisions. One of the issues was that the articles had left all decisions about slavery up to individual states, and the states had starkly different opinions on the issue. For example, Southern states reaped tremendous economic benefits from slavery and supported it, while some Northern states had already abolished it.
Differing state views on slavery complicated the convention's question of how to organize state representation at the federal level. Representation based on population was a straightforward enough concept, but because slaves were not considered people (note that this systemic racism should not be taken lightly), it got tricky. Counting the slaves as members of a state’s population would mean that the Southern states had much more representation than the Northern states.
To compromise, the delegates agreed on what is called the “Three-Fifths Compromise.” In article I, section II of the constitution it was written that population would be counted by adding “the whole Number of free persons, including those bound to Service for a Term of Years, and excluding Indians not taxed,” plus “three fifths of all other Persons.” Since slaves were not free and not mentioned as an exception, they were counted as being “three-fifths of a person.”
The topics of the slave trade and escaped slaves were also discussed at the convention. Congress was given the power to ban the slave trade, but it was agreed that it would continue until 1808. The issue of escaped slaves was also discussed, as there was disagreement about what to do if a slave fled to a free state. To address this issue, the “Fugitive Slave Clause” was included in article IV, section II. This clause allowed slaves who escaped to be caught and returned to slavery, even if they had reached freedom.