On what date did delegates sign the U.S. Constitution at Philadelphia’s Independence Hall?

Delegates signed the U.S. Constitution on September 17, 1787, at Independence Hall in Philadelphia.

The signing concluded the Constitutional Convention, which had met for four months to design a stronger national government. Thirty-nine delegates signed the document, representing 12 states. Rhode Island had declined to send delegates to the convention.

The date is sometimes confused with July 4, 1776, when the Declaration of Independence was adopted, or with June 21, 1788, when New Hampshire became the ninth state to ratify the Constitution. Ratification, rather than signing, allowed the new governmental system to take effect.

The Constitution established institutions including Congress, the presidency, and the federal judiciary. It also included a process for amendment. The first ten amendments, known as the Bill of Rights, were ratified in 1791, four years after the original document was signed.