At Vacation on Sylt the guest is often made aware of the former affiliation of the Frisian Island to neighboring Denmark. The question "When did Sylt actually to Denmark?" is answered inconsistently, however. The reason is a complicated mixture of dynastic developments with elements of personal and real unions.
In addition, it must be taken into account that Sylt was divided under state law for centuries. The northern tip around List ("Listland") had been under the direct control of the Danish crown since at least the middle of the 14th century, while the rest of the island was under the control of the Duke of Schleswig. In 1460, King Christian I of Denmark became Duke of Schleswig in personal union, but this did not make Sylt an integral part of Denmark. Real divisions between later successors of Christian with the participation of the Holstein dukes followed in the 16th century.
It was not until 1713 that the territory of the Duchy of Schleswig was then once again entirely in the hands of the Danish kings in their function as dukes of Schleswig (and from 1773 also of Holstein). From the end of the 18th century, this personal union increasingly became a real union ("Danish total state"): The people of Sylt had become de facto Danish citizens. This development was reinforced after the suppression of the Schleswig-Holstein uprising in 1848-1851. In 1864, Denmark lost the duchies and thus all of Sylt as a result of the defeat in the war against Prussia and Austria.
