The Constitutional Convention lasted 116 days, from May 25, 1787, until Sept. 17, 1787. Throughout the course of the convention, the Constitution was rewritten many times, states USConstitution.net.
The Constitutional Convention took place in Philadelphia and was originally scheduled to begin on May 14, 1787. However, it took several days for all the deputies from the various states to arrive, so the convention couldn't start until a quorum was present, which occurred on May 25, 1787. George Washington, the representative from Virginia who would go on to be the first president of the United States, was the unanimous choice to preside over the convention.