The Danish ethnic minority in Southern Schleswig, Germany, has existed by this name since 1920, when the Schleswig Plebiscite split German-ruled Schleswig into two parts: Northern Schleswig, with a Danish majority and a German minority was united with Denmark, while Southern Schleswig remained a part of Germany and had a German majority and Danish and Frisian minority populations. One of the most common names they use to describe themselves is danske sydslesvigere (Danish South Schleswigians).
Denmark has continued to support the minority financially. Danish schools and organizations have been run in Flensburg since 1920, and since 1926 throughout the greater region. Before the adoption of the democratic Weimar Constitution it was not allowed to teach in another language than German in school (apart from religious education lessons).
Membership in the Danish minority has been fluid since 1920, as objective criteria such as language to distinguish a German Schleswigian from a Danish are not taken into account. German law prohibits government registration of persons due to their ethnic origins, besides, membership in Germany's ethnic minorities is based on self-identification as is generally the universal case with ethnicity. The first ethnic Danes settle in Southern Schleswig in the 7th century. One of the first Danish cities, Hedeby, were founded in about 800. The Danevirke between Hollingstedt og the Eckernförde bay was a Danish border wall towards Germany. Schleswig (Southern Jutland) was in the Viking Age still a direct part of the Kingdom of Denmark. First in the 13th century it became a fiefdom of Denmark. In the 17th, 18th and up to the 19th centuries there was a language shift from Danish and Frisian dialects to Low German and later to High German as common speech in Southern Schleswig. Many German-minded Schleswigians have therefore ethnic Danish roots. At the same time there grew a conflict between German and Danish National Liberals, that culminated in two German-Danish wars in the 19th century. After the Second Schleswig War Schleswig became for the first time part of a German state. After a plebiscite in 1920 Northern Schleswig was officially reunited with Denmark, while Southern Schleswig remained a part of Germany.