Formerly a Celtic region, this area was conquered by the Roman Empire under Emperor Augustus in about 12 BCE, whereafter it was part of the Germania Superior province. During the decay of the Empire, Alamanni tribes settled here; their territory was conquered by Francia under King Clovis I about 496. From 511 onwards the area belonged to the eastern part of Frankish Austrasia, that—as Rhenish Franconia—became part of East Francia according to the 843 Treaty of Verdun.