Eider (river) in the context of "Danish people"

The Danes were a North Germanic tribe inhabiting southern Scandinavia, including the area now comprising Denmark proper, northern and eastern England, and the Scanian provinces of modern-day southern Sweden, during the Nordic Iron Age and the Viking Age. They founded what became the Kingdom of Denmark. The name of their realm is believed to mean "Danish March", viz. "the march of the Danes", in Old Norse, referring to their southern border zone between the Eider and Schlei rivers, known as the Danevirke.

Jutland (/ˈdʒʌtlənd/), historically known as the Cimbrian Peninsula, is a peninsula in Northern Europe that forms the continental portion of Denmark and part of northern Germany (Schleswig-Holstein). It stretches from the Grenen spit in the north to the confluence of the Elbe and the Sude in the southeast. The historic southern border river of Jutland as a cultural-geographical region, which historically also included Southern Schleswig, is the Eider. The peninsula, on the other hand, also comprises areas south of the Eider: Holstein, the former duchy of Lauenburg, and most of Hamburg and Lübeck.

Jutland's geography is flat, with comparatively steep hills in the east and a barely noticeable ridge running through the center. West Jutland is characterised by open lands, heaths, plains, and peat bogs, while East Jutland is more fertile with lakes and lush forests. The southwestern coast is characterised by the Wadden Sea, a large, unique international coastal region stretching through Denmark, Germany, and the Netherlands. The peninsula's longest river is the Eider, which rises close to the Baltic but flows in the direction of the North Sea due to a moraine, while the Gudenå is the longest river of Denmark. In order for ships not having to go around the whole peninsula to reach the Baltic, the Kiel Canal – the world's busiest artificial waterway, crossing the peninsula in the south – was constructed.

Southern Schleswig (German: Südschleswig or Landesteil Schleswig, Danish: Sydslesvig; North Frisian: Söödslaswik) is the southern half of the former Duchy of Schleswig in Germany on the Jutland Peninsula. The geographical area today covers the large area between the Eider river in the south and the Flensburg Fjord in the north, where it borders Denmark. Northern Schleswig, congruent with the former South Jutland County, forms the southernmost part of Denmark. The area belonged to the Crown of Denmark until Prussia and Austria declared war on Denmark in 1864. Denmark wanted to give away the German-speaking Holsten and set the new border at the small river Ejderen. Prussian chancellor Otto von Bismarck concluded that this justified a war, and even proclaimed it a "holy war". He also turned to the Emperor of Austria, Franz Joseph I of Austria for help. A similar war in 1848 had gone poorly for the Prussians. With Prussia's modern weapons and the help from both the Austrians and General Moltke, the Danish army was destroyed and forced to make a disorderly retreat. The Prussian-Danish border was then moved from the Elbe up in Jutland to the Kongeåen creek.

After the First World War, two referendums decided a new border.The northern part reverted to Denmark as Nordslesvig (North Slesvig). But the middle and southern part, including Schleswig's only city, Flensburg, remained in Germany. In Denmark, the loss of Flensborg sparked a political crisis, Påskekrisen or the Easter Crisis of 1920. After the Second World War the area remained as German territory and, with Holstein, formed the new state of Schleswig-Holstein as a part of the Federal Republic of Germany (West Germany) in 1948.

The terms Danish March and March of Schleswig (German: Dänische Mark or Mark Schleswig) are used to refer to a territory in modern-day Schleswig-Holstein north of the Eider and south of the Danevirke. It was established in the Early Middle Ages as a March of the Frankish Empire to defend against the Danes. The term "Danish March" is a modern designation not found in mediaeval sources. According to the Royal Frankish Annals, the Danish King led his troops "into the March" in 828 (ad marcam). In the 852 Yearbook of Fulda, there is mention of a "Guardian of the Danish Border" (custodes Danici limitis).

In Old Norse, Denmark was called Danmǫrk, viz. the marches of the Danes. The Latin name is Dania.

Holstein (/ˈhoʊlstaɪn/; German: [ˈhɔlʃtaɪn] ; Northern Low Saxon: Holsteen; Danish: Holsten; Latin: Holsatia) is the region between the rivers Elbe and Eider. It is the southern half of Schleswig-Holstein, the northernmost state of Germany.

Holstein once existed as the German County of Holstein (German: Grafschaft Holstein; 811–1474), the later Duchy of Holstein (German: Herzogtum Holstein; 1474–1866), and was the northernmost territory of the Holy Roman Empire. The history of Holstein is closely intertwined with the history of the Danish Duchy of Schleswig (Danish: Slesvig). The capital of Holstein is Kiel.