Early Middle Ages
Under the Carolingian kings, the feudal system proliferated, and monasteries and bishopries were important bases for maintaining the rule. The Treaty of Verdun of 843 assigned the western part of modern Switzerland (Upper Burgundy) to Lotharingia, ruled by Lothair I, and the eastern part (Alemannia) to the eastern kingdom of Louis the German that would become the Holy Roman Empire. The boundary between Alamania, ruled by Louis, and western Burgundy, ruled by Lothar, ran along the lower Aare, turning towards the south at the Rhine, passing west of Lucerne and across the Alps along the upper Rhône to Saint Gotthard Pass.
Louis the German in 853 granted his lands in the Reuss River valley to the monastery of St Felix and Regula in Zürich (modern day Fraumünster) of which his daughter Hildegard was the first abbess. According to legend this occurred after a stag bearing an illuminated crucifix between his antlers appeared to him in the marshland outside the town, at the shore of Lake Zürich. However, there is evidence that the monastery was already in existence before 853. The Fraumünster is across the river from the Grossmünster, which according to legend was founded by Charlemagne himself, as his horse fell to his knees on the spot where the martyrs Felix and Regula were buried.