Four States of the United States of America style themselves Commonwealths: Massachusetts Kentucky Virginia Pennsylvania In addition two dependencies of the US, Puerto Rico and the Northern Mariana Islands, style themselves commonwealths.
Kentucky, Massachusetts, Pennslvania and Virginia can continue to call themselves commonwealths for as long as they choose, but the US Constitution defines them as states. There are therefore 50 States in the US.
In the United States of America four states style themselves Commonwealths. They are Kentucky, Massachusetts, Pennsylvania, and Virginia. In addition, two associated territories, Puerto Rico and the Northern Mariana Islands, are called commonwealths.