200 years ago Secularization changed the German Southwest. Following the Napoleonic wars, the buildings, landholdings and property of the monasteries and bishoprics passed into state ownership. The repercussions are felt up until today, as new uses had to be found repeatedly for most of the empty buildings. Reichenau was also affected by the closure of religious institutions and the takeover of church property.
After nearly 1,100 years of religious rule, the island of Reichenau fell to the state of Baden in 1802 during Secularization. The extensive monastery library, which was one of the largest in Europe in the early Middle Ages, contained manuscripts with miniature paintings of great artistic value from the high Middle Ages. These and the books were brought to libraries in Karlsruhe and Heidelberg. The monastery church (Klosterkirche) of Mittelzell became a parish church.
Because the Baden administration did not want to pay the cost of maintenance, part of the monastery buildings were demolished between 1812 and 1825. The church landholdings were divided up and sold. When the interest of the local residents in their own history and its evidence grew with the development of monument preservation in the 19th century, the value of the complex was recognized as an "antiquity of the fatherland". As no magnificent Baroque new buildings were erected on Reichenau Island, a unique ensemble of medieval church architecture has been preserved until today. This brought the island recognition as part of the UNESCO World Cultural Heritage program in 2000.