Kentucky (ⁱ/kɨnˈtʌki/), officially the Commonwealth of Kentucky, is a state located in the Upper South of the United States. Kentucky is one of four U.S. states constituted as a commonwealth (the others being Virginia, Pennsylvania, and Massachusetts). Originally a part of Virginia, in 1792 Kentucky became the 15th state to join the Union. Kentucky is the 37th most extensive and the 26th most populous of the 50 United States.