The United States Constitution was signed on September 17, 1787, at Independence Hall in Philadelphia. Thirty-nine delegates endorsed the document at the final session of the Constitutional Convention.
The convention met during the summer of 1787 to replace the Articles of Confederation, the country’s first national governing framework. Delegates debated representation, federal powers, taxation, trade, and the balance between national and state authority.
Signing the document did not immediately put it into effect. The Constitution required ratification by the states. New Hampshire became the ninth state to ratify it on June 21, 1788, meeting the required threshold, and the new federal government began operating in 1789.
The date is sometimes confused with Constitution Day, which also commemorates the signing. It is separate from Independence Day, July 4, and from the date the Bill of Rights was ratified, December 15, 1791.