The United States Constitution is generally considered to have gone into effect on March 4, 1789, when the new federal government under the Constitution officially began operations.

Key dates in effect

  • June 21, 1788 : New Hampshire became the ninth state to ratify the Constitution, which made the Constitution the official framework for the United States under Article VII.
  • March 4, 1789 : The new government under the Constitution formally began, as set by the Confederation Congress; this is the date most commonly treated as when the Constitution “went into effect” in practice.

Why there are two dates

Many historians and legal scholars distinguish between:

  • The date the Constitution became the official governing framework (upon ratification by nine states on June 21, 1788).
  • The date the institutions it created (Congress, presidency, etc.) actually started operating, which was March 4, 1789.

So, if someone asks “when did the US Constitution go into effect,” the most standard answer is March 4, 1789, but it was already legally established as the nation’s governing charter once the ninth state ratified it on June 21, 1788.