The United States Constitution was written in the year 1787. It was drafted during the Constitutional Convention held in Philadelphia, which convened from May 25 to September 17, 1787. The Constitution was signed on September 17, 1787. After being written, it went through a ratification process by the states and officially became the framework of the U.S. government when New Hampshire became the ninth state to ratify it on June 21, 1788. The Constitution then went into operation on March 4, 1789.