Given the increasing ore mining in the Lahn Valley, officials from Nassau and Prussia in 1841 made an inspection trip along the river from Marburg to the Rhine. The Prussians were the driving force behind river expansion projects, seeking to establish a connection between Wetzlar and their Rhine Province and to secure the iron ore supply for the growing industry in the Ruhr Valley. Until 1844, Hesse-Darmstadt also joined expansion efforts, while Hesse-Kassel declined participation. The participating governments agreed to make the Lahn passable as far as Gießen for boats that were significantly larger than the existing vehicles on the river. In Prussian territory, the work was largely completed by 1847, including construction of locks in Dorlar, Wetzlar, Wetzlar-Blechwalze, Oberbiel and Niederbiel. In Nassau's territory, locks were built at Löhnberg, Villmar, and Balduinstein, as well as the greatest technical achievement: the Weilburg ship tunnel. The river bank reinforcement and channel deepening along Nassau's section of the Lahn, however, was slow. Moreover, when the lock at Limburg fell short of the width contractually agreed upon, Nassau refused an extension. This led to several clashes between Nassau and Prussia in the following years until Nassau had finally fulfilled its obligations in 1855.