According to the story of Saint Fridolin, St. Hilarius appeared to him in a dream, and commanded him to proceed to an island in the Rhine, in the territories of the Alamanni.

In obedience to this summon, Fridolin repaired to the "Emperor" Clovis, who granted him possession of the still unknown island, and thence proceeded through Helion, Strasburg, and Coire, founding churches in every district in honour of St. Hilarius.

[1] The only portion of the life that can be regarded as historically tenable, is that Fridolin was an Irish missionary, who preached the Christian religion in Gaul, and founded a monastery on the island of Säckingen in the Rhine; the exact dates of this are unknown.

On 10 February 878, the Emperor Charles the Fat gave his wife Richardis the monasteries of Säckingen, of St. Felix and of Regula in Zurich as a royal estate.

In 1173 Emperor Frederick Barbarossa granted rights to the Imperial bailiwick of Säckingen Abbey to Count Albert III of Habsburg.