Only twenty years later, though, the political landscape changed drastically with the French Revolutionary Wars. France annexed the Rhine’s left bank in 1797. In 1801, Leisel became the seat of a "mairie" (“mayoralty”), which persisted until 1840, well after the end of French rule. It comprised the villages of Siesbach, Leisel, Schwollen, Hattgenstein, Rinzenberg, Hambach, Böschweiler and Heupweiler. The political alignment changed once again with Napoleon's downfall and the Congress of Vienna, which grouped Leisel into the Grand Duchy of Oldenburg, or rather Oldenburg's local exclave, the Principality of Birkenfeld; most of Oldenburg's territory was in what is now northwest Germany, with a coastline on the North Sea. Oldenburg sovereignty is commemorated in the road name "Peterstraße" in the Leisel Forest. Grand Duke Peter had it built so that he did not have to travel through the Kingdom of Prussia, with whom he had ongoing border disputes, whenever he visited the "Birkenfelder Land".