The Constitutional Convention reached a quorum and began meeting in Philadelphia on May 25, 1787.
The convention had been scheduled to open on May 14, but too few state delegations had arrived. A quorum of seven states was finally present on May 25, allowing the delegates to conduct official business. The meetings took place in the Pennsylvania State House, now known as Independence Hall.
The convention had originally been called to revise the Articles of Confederation. Instead, the delegates developed an entirely new constitutional framework. George Washington was chosen as presiding officer, and the convention conducted its debates in secrecy so delegates could negotiate without immediate public pressure.
The work continued through the summer. The delegates signed the completed Constitution on September 17, 1787, and sent it to the states for ratification. May 25 is therefore the convention’s effective opening date, while September 17 is the signing date. Those dates are sometimes mistakenly treated as the same event.