During the summer of 1787, when the delegates to the Constitutional Convention met in Philadelphia, the issue of representation in Congress was strongly debated. Delegates from the large states favored the Virginia Plan's proposal for two houses of Congress with representation based on population. Delegates from the small states favored equal representation in a single house, as suggested by the New Jersey Plan. For two weeks in July, the delegates struggled in the hot Pennsylvania State House (now Independence Hall) to find an approach that all could agree upon. Finally, on July 16, the delegates adopted a group of resolutions that became known as the Great Compromise. The compromise meant that there would be an upper house in which the states would be equally represented and a lower house with representation based upon population as enumerated in a decennial census. This article describes the population estimates used by the Congress during the Constitutional Convention. Also included in this article are suggestions in teaching with documents.