There are currently four commonwealths in the United States: Massachusetts, Pennsylvania, Virginia, Kentucky. The only difference between commonwealths and states is the name. They simply decided to call themselves commonwealths instead of states. However, Puerto Rico is also a commonwealth. Key differences there: -The Internal Revenue Code does not apply to Puerto Rico. -Puerto Rico has no voting representation in Congress. -Puerto Rican citizens are not allowed to vote in presidential elections. Puerto Ricans are U.S. citizens; they pay social security, can receive federal welfare, and can serve in the armed forces. But they don't pay federal taxes, and they don't vote in presidential elections.

All of the fifty states are "states", as defined in the federal Constitution. Massachusetts, Virginia, Pennsylvania, and Kentucky are also commonwealths, because this is the official name used in their state Constitutions. So the simple answer is that commonwealths are commonwealths because they chose to be so, but let's try to understand why . . . it wasn't a choice that came out of nowhere. According to the website of the Secretary of the Commonwealth of Massachusetts: At the time of the American Revolution, "commonwealth" was a popular term for describing a state/nation where the people came together by mutual consent. It was a term with democratic overtones, in contrast to the monarchic system that the colonies were trying to throw off. John Adams put the word "commonwealth" into his 1780 draft of the Massachusetts Constitution and it was accepted, as opposed to earlier rejected versions that used the term "state". So that's why Massachusetts is a commonwealth. Given that Virginia and Pennsylvania would have written their Constitutions around the same time, a similar idea might have factored in for them. Kentucky came later, so it's anyone's guess, but it's still one of the older states... it seems possible that the same idea could apply. I hope this answers the question. I'll leave you with a slightly related bit of trivia: the official name of Rhode Island is actually "The State of Rhode Island and Providence Plantations". Our smallest state is composed of what were originally (albeit briefly) two separate territories.

The word 'commonwealth' is defined as an independent state or community, especially a democratic republic. So I pressume that a commonwealth state is one that has its own government and laws, in oppose to one that relies entirely upon the laws of the United States.

Legally, there is no difference between a state and the four commonwealths, Massachusetts, Pennsylvania, Virginia, Kentucky.

According to what I learned in undergraduate school and Law School in the Grand and Glorious Commonwealth of Massachusetts, there is a difference between a State and a Commonwealth. A State is a political subdivision of the Federal Government and only has the rights granted by the United States Constitution. A Commonwealth is an independent and sovereign entity that voluntarilty joins the Union, but retains its own identity. For all intents and purposes, in the modern age, there is little practical difference. This is just a historical footnote now.