On July 11, 1870 the section of line was opened from Neuwied to Oberkassel, where the Bonn–Oberkassel train ferry provided a connection between the West Rhine and East Rhine lines. In addition, the line from Friedrich-Wilhelms-Hütte to Siegburg had already been completed; the complete opening of the line only awaited the completion of the Sieg bridge. During the Franco-Prussian War, the line was of great strategic importance as a supply route. As a result, the building of the Sieg bridge was accelerated with extra workers, starting in the late summer of 1870. The whole route was opened on March 1, 1871. At the same time a branch was opened from Friedrich-Wilhelms-Hütte to Troisdorf and the line to Cologne, which would later become the main line.