There were two main issues that created a great deal of debate and a need for compromise at the Constitutional Convention in Philadelphia in 1787. The first of these issues was slavery and the second was representation in the Congress.
The issue of representation in Congress pitted the states with larger populations against the states with small populations. The states with larger populations wanted Congress to be apportioned based on population. In other words, they thought that they should have more votes in Congress because they had more people. By contrast, the smaller states wanted each state to have an equal number of votes in Congress. They felt that all of the states were equally important and should have an equal say. This debate led to the Great Compromise which set up a bicameral Congress in which the House of Representatives was apportioned on the basis of population and the Senate had equal representation for each state.
The second issue was slavery. Slavery created disputes between the North and the South. There were two main issues. First was the issue of the slave trade. The North wanted it banned and the South did not. They compromised, saying that the slave trade could not be banned until 20 years after the ratification of the Constitution. Second was the issue of slave populations and representation. As we saw in the previous paragraph, the House of Representatives was apportioned on the basis of population. The Southern states wanted slaves to be counted in their populations. The North felt this was absurd as the slaves were not allowed to vote and were deemed to be property. The two sides had to compromise on this as well. They created the “Three-fifths Compromise,” in which 3/5 of the population of slaves were counted for the purposes of deciding how many representatives a state should get in the House of Representatives.