May 25, 1787: The Constitutional Convention opens with a quorum of seven states in Philadelphia to discuss revising the Articles of Confederation. Eventually, all states but Rhode Island are represented.
Sept. 17, 1787: All 12 state delegations approve the Constitution, 39 delegates sign it of the 42 present, and the Convention formally adjourns.
June 21, 1788: The Constitution becomes effective for the ratifying states when New Hampshire is the ninth state to ratify it.
Mar. 4, 1789: The first Congress under the Constitution convenes in New York City.
Sept. 24, 1789: Congress establishes a Supreme Court, 13 district courts, three ad hoc circuit courts, and the position of Attorney General.
Sept. 25, 1789: Congress approves 12 amendments and sends them to the states for ratification.
Feb. 2, 1790: Supreme Court convenes for the first time after an unsuccessful attempt on February 1.
Dec. 15, 1791: Virginia ratifies the Bill of Rights, and 10 of the 12 proposed amendments become part of the U.S. Constitution.