The United States Constitution was signed on September 17, 1787, at the Constitutional Convention commemorated by America250.
The signing took place at the Pennsylvania State House in Philadelphia, later renamed Independence Hall. Thirty-nine delegates endorsed the document at the convention’s final session, after months of debate over representation, executive power, taxation, and the balance between state and national authority.
The convention had begun on May 25, 1787, after enough delegates arrived to establish a quorum. Although the meeting was initially called to revise the Articles of Confederation, the delegates ultimately drafted an entirely new governing framework.
September 17 is now observed in the United States as Constitution Day and Citizenship Day. The date is sometimes confused with July 4, 1776, when the Declaration of Independence was adopted, or with March 4, 1789, when the Constitution’s federal government began operating.