city, Schleswig-Holstein Land (state), northern Germany. The city forms a semicircle around the head of the Schlei, a narrow inlet of the Baltic Sea that affords access to small vessels, northwest of Kiel. First mentioned in 804–808 as Sliesthorp (and later as Sliaswich), the town was in the area of Haddeby (ancient Norse: Haithabu), an important Baltic–North Sea trade centre from the 9th to the 11th century. St. Ansgar built the first church there in 850, and the town became a bishopric in 947. Schleswig's oldest surviving charter, from 1250, refers to an earlier charter. Its Gottorp Castle was the residence of the dukes of Schleswig and later (until 1713) of the dukes of Schleswig-Holstein-Gottorp, but its trade dwindled because of the rivalry of the Hanseatic town of Lübeck, local wars, and the silting up of the Schlei. Schleswig was the seat of the Danish governor of the duchies of Schleswig and Holstein (1721–1848) and was the capital of the Prussian province of Schleswig-Holstein from 1867 to 1918. When Kiel was made the capital of Schleswig-Holstein Land after World War II, Schleswig received as compensation the state supreme court, the state museum, and the state archives.

Services are significant for the local economy, and there is a modest manufacturing sector that produces electronic equipment, adhesive products, and beer. Gottorp Castle is home to two Land museums (for archaeology and for art and culture); the most famous exhibit is the Nydamboot (Nydam boat), a 4th-century Viking ship discovered in 1863 in the Nydam marsh. St. Peter's Cathedral (mainly 13th century) has a magnificent altarpiece, known as the Bordesholm Altar, carved by Hans Brüggeman in 1514–21. Pop. (2003 est.) 24,288.

historic and cultural region occupying the southern Jutland Peninsula north of the Eider River and now encompassing the northern half of Schleswig-Holstein Land (state) in northern Germany and Sønderjylland amtskommune (county commune) in southern Denmark. Schleswig became a Danish duchy in the 12th century and remained a fief associated with Denmark until it was forcibly annexed by Prussia and incorporated with Holstein as a single Prussian province in 1866. Following World War I the Danish majority living in North Schleswig (north of Flensburg) voted for incorporation with Denmark in a plebiscite (1920) held in accordance with the Treaty of Versailles.

Evidence of the struggle between the Danes and Germans from the 9th to the 12th century lies west of the town of Schleswig. Here the Danish kings built an impressive fortification wall known as the Danewerk. Nearby are the ruins of Haithabu, a historic Viking trading settlement. Evidence of both German and Danish cultural influences abound throughout Schleswig. Scandinavian place-names are mixed with German names throughout the lands north of the Eider, where dispersed farms and small hamlets are predominant. Danish farms, however, do not extend south of the city of Schleswig. The area from Schleswig north to Flensburg has a mixture of Saxon and Danish farmhouses, while north of Flensburg the Jutish rectangular enclosed farmstead is most common. The majority of the people in the German portion of Schleswig speak a Low German dialect, while the majority in the Danish portion of the region speak Danish. More than 85 percent of the region's total population are Protestants.