Why Pennsylvania Is Called the Keystone State—Not the Keystone Commonwealth
Pennsylvania is famously known as “The Keystone State,” a nickname deeply rooted in both symbolism and history. But for a state that officially identifies as a Commonwealth, the inconsistency in terminology raises a natural question: Why not the Keystone Commonwealth?
To answer that, we first have to understand what a keystone is—and then how Pennsylvania earned its place as one.
What Is a Keystone?
A keystone is the central, wedge-shaped stone at the top of an arch that holds all the other stones in place. Without it, the entire structure would collapse. In architecture, it’s both structurally and symbolically essential: small in size, massive in importance.
This idea—of holding the whole thing together—became a powerful metaphor in the founding of the United States.
Pennsylvania’s Role as the Keystone
Pennsylvania occupied a literal and figurative middle position among the original 13 colonies. Geographically, it sat in the center of the Eastern Seaboard, bordering both Northern and Southern colonies. Politically and ideologically, it often acted as the bridge between rival factions during the founding of the country.
During the American Revolution and Constitutional Convention, Pennsylvania played a stabilizing role. Philadelphia served as the meeting ground for the First and Second Continental Congresses and as the nation’s capital for a time. The Declaration of Independence and the U.S. Constitution were both signed in Independence Hall.
Just as the keystone in an arch keeps the whole structure together, Pennsylvania helped unify a fragile coalition of colonies into a single nation.
Commonwealth vs. State: What’s the Difference?
The term Commonwealth is more ceremonial than functional. Pennsylvania is one of four U.S. states—along with Massachusetts, Virginia, and Kentucky—that call themselves commonwealths. The word reflects a focus on the common good, derived from British legal tradition.
But “commonwealth” doesn’t change the legal standing of Pennsylvania. It’s still a state by all federal definitions. The phrase “Keystone Commonwealth” may be technically accurate, but it never caught on in the public imagination.
Why Not “The Keystone Commonwealth”?
Language favors rhythm and clarity. State is short, punchy, and familiar. Keystone State rolls off the tongue. By contrast, Keystone Commonwealth is clunkier, more abstract, and less recognizable.
There’s also tradition. The phrase “Keystone State” dates back to at least the early 1800s and became widely used during the Civil War and in political speeches thereafter. It was already baked into maps, slogans, and symbols long before the nuances of the word commonwealth mattered to anyone outside a legal dictionary.
Final Thought
So why is Pennsylvania the Keystone State and not the Keystone Commonwealth? Because its nickname honors its central role in America’s formation—and because, in the court of public language, simplicity wins. The keystone metaphor stuck because Pennsylvania was essential. And the label state stuck because it’s what people say.