Britannica
Sources used in this answer
- 26 Decade-Defining Events in U.S. History - 1780s: Constitution of the United States of America (1787)
- Constitution of the United States of America - Constitutional Convention
- Text of the Constitution of the United States
- United States - Constitutional framework
- Continental Congress
- Constitutional Convention
When did the U.S. Constitution enter into force?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
The U.S. Constitution formally entered into force on March 4, 1789, the date established by Congress for the new government to commence proceedings.12
While the document was signed by 39 delegates on September 17, 1787, it required ratification by nine states to become effective. This threshold was reached on June 21, 1788, when New Hampshire became the ninth state to ratify the Constitution of the United States. The government subsequently began operations in 1789, marked by the swearing-in of George Washington as the nation's first president.12