Source of the Danube
As early as 1847 the following definition can already be found in the "Universallexikon des Großherzogtums Baden" (Universal Lexicon of the Grand Duchy of Baden): “Danube, the biggest river of Germany, rises at the Martinskapelle in a wild and lonely area of the Black Forest, is called Brege at its origin and forms the river Danube in Donaueschingen where it is unified with the Brigach." (German original: „Donau, der größte Fluß Deutschlands, entspringt bei der Martinskapelle in einer wilden und einsamen Gegend des Schwarzwaldes, heißt am Anfang Brege… und bildet erst in Donaueschingen, wo sie sich mit der Brigach vereinigt, die Donau.“)
Source of the Danube
There was an active rivalry between the municipalities of Furtwangen and Donaueschingen for the claim of being home to the "official" source of the Danube since the 1950s, sometimes with the involvement of the government of the state of Baden-Württemberg. 
Thus, in 1981 the state government granted Donaueschingen the request that the source in Furtwangen should no longer be labelled "Donauquelle" in official maps.