The significant political document drafted during the summer of 1787 in Philadelphia is the U.S. Constitution. This document established the framework for the United States government, laying out the structure of the legislative, executive, and judicial branches. It aimed to create a strong federal government while balancing the rights of individual states. The Constitution also included the Bill of Rights, which safeguarded individual liberties. Its ratification marked a critical turning point in American history, enabling the nation to better address governance challenges and conflicts following independence.