Originally, the term referred to the central of the three Saxon tribes north of the River Elbe: Tedmarsgoi (Dithmarschen), Holstein and Sturmarii (Stormarn).

The southern border of the Angles was marked by the marshes surrounding the Eider, that combined with the dense old-growth forrest to the south of the river, formed a natural barrier.

Originally built as a dyke, it was gradually expanded into a 30-kilometer earthwork with a palisade fortification, forming a barrier between the Danes and their southern neighbors.

The Danevirke was strategically positioned at the most narrow point of the peninsula, with its eastern end beginning at the Treene River and extending to the Schlei Bay.

[13] The establishment of the Danevirke not only helped to prevent Saxon and Wagrian raids into Danish territory but also served as a toll station.

Danish chieftains would collect fees from traders, merchants, and peasants traveling along the Hærvejen (Heerweg/Armyway), the main trade route running through the peninsula.

Saxons, Wagrians, and Danes alike used the Hærvejen to trade goods such as honey, furs, amber, glass, metalwork, and other commodities, such as livestock, with cattle and oxen being particularly important.

[citation needed] Normalcy in the area vanished with the expansion of the Frankish Empire into Saxony from 772 to 804, triggering a generational war on an unprecedented scale for the region.

This conflict, fueled by Charlemagne's desire to conquer the Saxons and convert them from their belief in the Germanic pantheon to Christianity, used the Deventer raid as a pretext to wage a war that would ultimately reshape the political and cultural landscape of what would later become Holstein forever.

[citation needed] In retaliation for the raid on the church in Deventer, Charlemagne ordered his troops to destroy the holy pillar Irminsul, near Paderborn in either 772 or 773—a notorious act that sent shockwaves throughout the Germanic pagan world.

[citation needed] For centuries, the Danes and Saxons had regarded each other as kindred peoples, sharing the same belief in the Germanic pantheon and frequently intermarrying, especially among the elite.

[citation needed] In response to the Danes' involvement in the war, Charlemagne seems to have recruited the Obotrites by promising them the Saxon portion of Holstein.

Between 500 and 1200, Schleswig was an integral part of Denmark, but during the 12th century, Duke Abel of Schlewig came into conflict with his brother King Eric IV.

[citation needed] Following the Protestant Reformation, German was established as the language of commerce, administration, education, and clergy in Schleswig despite the population being ethnically Danish.

As a result, Danish students, future administrators, clergy, and educators were taught in German and continued to use the language throughout their professional lives.

As a result, a language shift slowly began forming in South Schleswig and gradually spread north, which alarmed Copenhagen.

Therefore, the Danes sought to reintegrate Schleswig into the Kingdom of Denmark, reversing the separation created by King Abel, while also granting Holstein independence to join the German Confederation as a sovereign entity.

[citation needed] Contrary to the hopes of German Schleswig-Holsteiners, the area did not gain its independence, but was annexed as a province of Prussia in 1867.

During the decades of Prussian rule within the German Empire, authorities attempted a Germanisation policy in the northern part of Schleswig, which remained predominantly Danish.

[citation needed] Following the defeat of Germany in World War I, the Allied powers arranged a plebiscite in northern and central Schleswig.

The plebiscite was conducted under the auspices of an international commission which designated two voting zones to cover the northern and south-central parts of Schleswig.

[citation needed] In 1955, the German and Danish governments issued the Bonn-Copenhagen Declarations confirming the rights of the ethnic minorities on both sides of the border.

Written either below or to the right of the lion and the nettle is "Schleswig-Holstein" below which either the Name of the agency using the logo is shown or the motto "Der echte Norden" (Germany's true North).

As is the case throughout Germany, High German, introduced in the 16th century, has come to steadily replace local dialects for official purposes, and is today the predominant language of media, law and legislature.

Since the end of World War II and widespread adoption of TV, radio and other mass media, it has gradually come to supplant local dialects in urban areas as well.

[41] In 2014, Schleswig-Holstein became the first German state to cover 100% of its electric power demand with renewable energy sources (chiefly wind 70%, solar 3.8%, and biomass 8.3%).

[43] The largest German oil field Mittelplate is located in the North Sea off the Dithmarsch coast and connected with refinery in Hemmingstedt and chemical plants in Brunsbüttel via pipeline.

The reported discovery of small spherical beads of nuclear material in the area led to further concern, as well as the presence of minute amounts of plutonium in the Elbe.

The nuclear plants have further been questioned as a source of the cases due to comparison to the Savannah River Site in the United States.

Intriguingly, a larger case-control study in Lower Saxony found a correlation between the "untrained immune system" (as judged as contact with other children, vaccinations, etc.)