Only during the 1930s, when Sylt was fortified by the military, did the number of inhabitants rise briefly (1939: 306, half of which belonged to the Reichsarbeitsdienst).

Until the Nössedeich was constructed in 1936/37, the area was liable to flooding which destroyed both harvests and homes.

Raised areas that served as dwelling sites such as the Firstklent, were excavated in 1969-73 by Joachim Reinstein, yielding findings from the Stone and Bronze Age.

The last visible remains of the so-called Archsumburg (a circular rampart with an internal diameter of roughly 65 metres, built around 2,000 years ago) were probably removed around 1860.

In separate referendums in 2008, Westerland (by a large majority) and Sylt-Ost (narrowly) agreed to the merger in May 2008.

Sylter Verkehrsgesellschaft [de] operates buses that provide public transport on the island.