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.
Up until Secularization Allerheiligen was the religious and cultural center of the region. The monastic community primarily devoted itself to teaching, the sciences and spiritual guidance. The medieval monastery school had developed to a well-known "Gymnasium" (secondary school) over the course of time.
Margrave Karl Friedrich of Baden closed the Allerheiligen Abbey on 29 November 1802; the monks lost their livelihood. The landholdings were sold and furnishings in good condition were taken to Karlsruhe. All attempts to use the monastery again failed: A "place of correction for worldly priests with a wicked past “ was to be housed here, however a fire destroyed part of the complex in 1804. The manufacturer Brenneisen began to set up a wool manufactory in one of the undamaged buildings, however he abandoned this undertaking in 1806.
Allerheiligen gradually decayed, as the Baden dynasty provided no funds for its upkeep. In 1811 it sold the building for demolition, and in the years that followed the enclosure was torn down. Church services were celebrated in the church until its demolition in 1819, and it then served as a quarry. The remains of the church have been preserved as a romantic ruins and have managed to find a "use" – by the new Black Forest tourism!