The U.S. Constitution took effect as the nation’s governing framework in 1789.
The Constitution was drafted and signed in Philadelphia on September 17, 1787, but signing did not immediately replace the Articles of Confederation. The new document required ratification by nine states before it could establish the new federal government.
New Hampshire became the ninth state to ratify it on June 21, 1788. The federal government officially began operating under the Constitution on March 4, 1789, when the First Congress convened in New York City. George Washington was inaugurated as the first president on April 30, 1789.
A common mix-up is treating 1787 as the Constitution’s effective year. 1787 is the year of drafting and signing; 1789 marks the start of constitutional government. The document has since been amended 27 times.