Delaware was the first state to ratify the U.S. Constitution, doing so on December 7, 1787.
Delaware's ratifying convention approved the Constitution unanimously, with a vote of 30–0. Its early approval earned the state the nickname “The First State,” a title still used officially and popularly.
Article Seven of the Constitution required approval by conventions in nine states before the document could take effect. Delaware acted first, followed by Pennsylvania five days later. New Hampshire became the crucial ninth state on June 21, 1788, putting the Constitution into operation.
Delaware's action did not mean the Constitution immediately governed every state. Ratification continued afterward: Rhode Island was the last of the original thirteen states to approve it, on May 29, 1790. The first state to ratify is therefore different from the ninth state that made the Constitution effective and the last state to join the original ratification process.