North and South Carolina, Virginia and West Virginia, North and South Dakota, why do these states share names and what stopped them from being changed to something not already in use?
They used to be the same territories/states but split. Virginia encompassed all of Virginia and West Virginia until WV independence in 1863. North Dakota and South Dakota were together as the Dakota Territory until 1889. The carolinas were one big territory with separate institutions in the north and south but became two colonies in the 1720s. In all of these cases, both halves of the former states/territories liked the names they had and preferred the continuation of their old name with the geographic prefix.