The Great Compromise at the Constitutional Convention ended the debate over congressional representation by establishing a two-branch legislature with each state represented equally in the Senate, and proportionately by population in the House of Representatives. Its debate also addressed how slaves would be counted toward a state's population.
At the 1787 Constitutional Convention, larger states favored congressional representation based on population, but smaller states wanted equal representation. James Madison and Edmund Randolph proposed the Virginia Plan, which outlined a legislative branch with two houses, both with representation based on population. William Patterson proposed the New Jersey Plan, which featured a legislature with one house in which each state got one vote, essentially the same system that existed under the Articles of Confederation. Progress stalled until Roger Sherman proposed the Great Compromise, also known as the Connecticut Compromise, in which each state would send two representatives to the Senate and one representative for every 30,000 people to the House.
Once representation was decided, the debate turned to whether to include slaves in a state's population count and eventually led to the Three-Fifths Compromise that allowed states to count three-fifths of its slaves toward its total population. Prior to this compromise, slave-holding states wanted to increase their representation in the House by including all slaves in their population count. Opponents argued that slaves had no rights as citizens and therefore should not be counted toward representation.