Pennsylvania, officially the Commonwealth of Pennsylvania, is a state located in the northern and Mid-Atlantic regions of the United States. The Appalachian Mountains run through its middle. Pennsylvania, the 33rd largest, the 6th most populous, and the 9th most densely populated of the 50 United States, is one of the 13 original founding states; it came into being in 1681 as a result of a royal land grant to William Penn, the son of the state's namesake. Philadelphia, the Keystone State’s largest city, displays its rich history in Independence Hall (where the Declaration of Independence and Constitution were signed) and the Liberty Bell, an enduring symbol of American freedom.