In the 9th century, the monk St. Meinrad, of the family of the Counts of Hohenzollern, left one of the local monasteries to built a hermitage in the wilderness of today's Einsiedeln. He took with him a miracle-working statue of the Virgin Mary given to him by the Abbess Hildegarde of Zürich. He soon became well-known in the local village for his kindness and holiness, and received many visitors and gifts.
On January 21, 861, two thieves murdered Meinrad for the treasure in his hermitage. According to legend, the murderers were apprehended after two ravens followed them into town and drew attention to them with loud squawking.
In 940, a few Benedictine monks turned Meinrad's little hermitage into the "Lady Chapel." The chapel is said to have been consecrated by Christ himself on September 14, 948.
The bishop who was to consecrate the new site had a vision in which the church was filled with a brilliant light as Christ approached the altar; the next day, when he went to perform the ceremony, he heard a voice saying the chapel had already been divinely consecrated. The miracle was confirmed by Pope Leo VIII 16 years later in a papal bull.
St. Meinrad had the Black Madonna statue (its dark color caused by years of candle smoke) as part of his altarpiece; it was placed in the Lady Chapel for veneration after his death. Many miracles were attributed to the intercession of "Our Lady of Einsiedeln," and pilgrimages to Einsiedeln began shortly after 1000 AD.
[Source - Sacred Destinations]