Delegates signed the United States Constitution on September 17, 1787, at Independence Hall in Philadelphia.
The signing occurred at the final session of the Constitutional Convention. Thirty-nine delegates endorsed the document, which created a new framework for the federal government and replaced the Articles of Confederation after ratification by the states.
September 17 is now observed as Constitution Day and Citizenship Day in the United States. It is sometimes confused with other important constitutional dates. The Constitution was presented to the Confederation Congress on September 28, 1787, and New Hampshire became the ninth state to ratify it on June 21, 1788, making the document effective under Article VII.
The Constitution’s 250th signing anniversary will occur in 2037, eleven years after America250. That later milestone is distinct from the 2026 semiquincentennial, which commemorates the Declaration of Independence and the creation of the United States as an independent country.