The United States Constitution was written during the Philadelphia Convention, also known as the Constitutional Convention, which convened from May 25 to September 17, 1787. The Constitution was signed on September 17, 1787, in Philadelphia, Pennsylvania. After its signing, it was sent to the states for ratification, which was completed on June 21, 1788, when New Hampshire became the ninth state to ratify it. The Constitution then went into effect, and the new government began operating under it on March 4, 1789.
