Actually there aren't... at least, not technically. Each of the four states of Kentucky, Massachusetts, Pennsylvania and Virginia are officially designated with the prefix "The Commonwealth of...". While still considered to be states in every other respect, they remain unique in that none of the other 46 states refer to themselves in any way other than as states. This "commonwealth" designation has no legal impact and in the context of these four states - each being among the first 15 states to join the union - the term merely refers to the common welfare of the state's people and was originally engaged to emphasise "government based on the common consent of the people", as distinct from anything to do with their previous status as royal colonies of Great Britain. As well as Kentucky, Massachusetts, Pennsylvania and Virginia, the states of Vermont and Delaware also refer to themselves as a "commonwealth" in their constitutions, although in both cases the term is used interchangeably with the term "state" and neither state formally adopted "The Commonwealth of..." prefix as an official designation. But wait, there's more...