The Constitutional Convention met in Philadelphia in 1787. There was no precedent for the undertaking, so a number of divisive issues had to be dealt with.
The first important and divisive issue was whether to amend or replace the Articles of Confederation. The first government of the United States was based on the Articles of Confederation, but they proved to be inadequate for several reasons. The biggest problem with the Articles was the weakness of the central government. The individual states retained too much power, and the national government was virtually impotent. Shay's Rebellion, which was symptomatic of the country's financial problems, showed that the status quo could not be maintained. Therefore, the Founding Fathers decided to write a new document. Some feared that they had exceeded their authority in doing so.
Perhaps the biggest controversy was over the issue of representation. Under the Articles, all states had had one vote. This arrangement favored the smaller states. At the Philadelphia convention, the large states sought a national legislature based on states's populations. But the small states did not want to relinquish the power they had enjoyed under the Articles. After much contentious debate, the Connecticut Compromise gave the large states more representation in the House, and it allowed each state an equal voice in the Senate.
Another contentious issue was over voting. How would the new nation's representatives, senators, and presidents be selected? Only the representatives in the House would be elected by popular vote. In those days, that meant only white men who paid taxes could vote. Senators and presidents were to be elected by the state legislatures and the Electoral College, respectively.
Slavery could have become a divisive issue. But the Founding Fathers, rightly or wrongly, chose not to let slavery become a key issue in Philadelphia. They feared a debate over slavery would jeopardize the work of producing a new constitution.