From the end of the 18th on into the latter half of the 19th century, the Castle Mill's ownership history raises more questions than it answers: on 21 October 1793, French Revolutionary troops occupied Electoral Mainz; on 4 November 1797, France annexed the Rhine's left bank; on 9 February 1801 the German Empire ceded the area to France in the Treaty of Lunéville. Noble and ecclesiastical holdings were seized for the French State and publicly auctioned. Whether or not the Castle Mill met with this fate, it was restored on 25 June 1804 by Napoleon to Count Philipp Franz von der Leyen (d. 1829), and he later sold it – no later than 1820 – when the prince was getting rid of his last holdings on the Middle Rhine, only to acquire Schloss Waal (a castle in Ostallgäu) a few years later.