Pennsylvania becomes the second state to ratify the US Constitution.

Pennsylvania, officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, Maryland to its south, West Virginia to its southwest, Ohio and the Ohio River to its west, Lake Erie and New York to its north, the Delaware River and New Jersey to its east, and the Canadian province of Ontario to its northwest via Lake Erie. Pennsylvania's most populous city is Philadelphia, while the capital of the state is Harrisburg. It is the fifth-most populous U.S. state, with over 13 million residents as of the 2020 United States census, as well as being the ninth-highest by population density and the 33rd-largest state by land area. The largest metropolitan statistical area is the southeastern Delaware Valley, including and surrounding Philadelphia, the state's largest and nation's sixth-most populous city. The second-largest metropolitan area, Greater Pittsburgh, is centered in and around Pittsburgh, the state's second-largest city.

The Constitution of the United States is the supreme law of the United States of America. It superseded the Articles of Confederation, the nation's first constitution, on March 4, 1789. Originally including seven articles, the Constitution delineates the frame of the federal government. The Constitution's first three articles embody the doctrine of the separation of powers, in which the federal government is divided into three branches: the legislative, consisting of the bicameral Congress ; the executive, consisting of the president and subordinate officers ; and the judicial, consisting of the Supreme Court and other federal courts. Article IV, Article V, and Article VI embody concepts of federalism, describing the rights and responsibilities of state governments, the states in relationship to the federal government, and the shared process of constitutional amendment. Article VII establishes the procedure subsequently used by the 13 states to ratify it. The Constitution of the United States is the oldest and longest-standing written and codified national constitution in force in the world.

December 12 is the 346th day of the year in the Gregorian calendar; 19 days remain until the end of the year.