IN early America, Pennsylvania played a vital geographic and strategic role in holding together the states of the newly formed Union.
Pennsylvania's slogan is life, liberty and the pursuit of happiness. Its founding father was William Penn, English religious and social reformer.National Guard secures Philadelphia City Hall in Philadelphia, PennsylvaniaCredit: Getty Images - Getty
Why is Pennsylvania called a commonwealth, and not a state?
Pennsylvania is officially a Commonwealth, a word which comes from Old English and means the "common weal" or well-being of the public.
The term harks back to the area's constitution, which "simply deems it as such", says the Merriam-Webster dictionary.
Apparently the term 'commonwealth' was preferred by a number of political writers in the 1700s.
This was due to there being "some anti-monarchial sentiment in using the word 'commonwealth'."
In Pennsylvania, all legal processes are carried out in the name of the Commonwealth, although the word does not appear on the State Seal.Punxsutawney's Groundhog legend pre-dates the area's first white settlers in Pennsylvania
What's the difference between a commonwealth and a state?
The distinction between 'commonwealth' and 'state' is in name alone, explains the Merriam Webster dictionary.
It adds: "The commonwealths are just like any other state in their politics and laws.
"There is no difference in their relationship to the nation as a whole."Protesters urge outside the Pennsylvania State CapitolCredit: AP:Associated Press
Which other states are known as commonwealths?
Kentucky, Massachusetts, Pennsylvania and Virginia are four states in the US which call themselves commonwealths.
What about Puerto Rico and Northern Mariana Islands?
The US has two other commonwealths - Puerto Rico and the Northern Mariana Islands.
"But they are of a different kind. They are not states, and have only a non-voting representative in Congress," explains Merriam-Webster.
"While residents of these islands have US citizenship, they pay no federal income taxes - though they pay other kinds of federal taxes," it adds.