This dispute was finally settled after World War I: The Danish-German border which had been moved north to the Kongeå after the Prussian-Austrian conquest in 1864 was relocated south to its present location between Kongeå and Eider. The southern, German part of Schleswig was by then mostly German-speaking and identifying as German and remained part of the Province of Schleswig-Holstein.
This dispute was ultimately resolved after World War I: The Danish-German border, which had been shifted north to the Kongeå following Prussian-Austrian conquest in 1864, was relocated south to its current position between Kongeå and Eider. The southern, German part of Schleswig, by then predominantly German-speaking and identifying as German, remained a part of the Province of Schleswig-Holstein.