It is unclear from what the name Keitum (Kairem in North Frisian, Kejtum in Danish) is derived.

Although keeping the navigation channel open was a continuing problem, Keitum harbour was the main connection between Sylt and the mainland until around 1867.

Keitum is known for its large number of traditional Uthland-Frisian houses, many of them over 200 years old, and its tree-lined avenues.

In addition, many craftspeople (like gold smiths, weavers and potters) are based in Keitum.

[1]: 189–190 Originally built in the early 13th century, this Romanesque church is today thought to be the oldest in Schleswig-Holstein.

[1]: 330 The attached graveyard holds the graves of numerous important local families (especially whalers and other owners or masters of ships) and of some notable people: Rudolf Augstein, Gerhard Schröder, Uwe Dallmeier [de], Peter Suhrkamp and Ernst Mollenhauer [de].

In World War II, an observation post was situated on the hill, damaging the site.

The former is a house built in 1739 and mostly retains period furniture and accessoires, exhibiting 18th century home decor and living styles.

The Sylt Museum is located in a house dating from 1759 and features exhibits on local history and regional living conditions in the past.

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