The first ten kilometres of the Neudietendorf-Ritschenhausen line was built by the Thuringian Railway Company () in 1867 as a branch line from Neudietendorf to Arnstadt. In 1879, the line was extended via Plaue to Ilmenau (Erfurt-Ilmenau line). Work on the crossing of the Thuringian Forest and the closing of the gap between Plaue and Ritschenhausen was started in 1879 by the Prussian state railways. Three years later, the Suhl-Grimmenthal section was inaugurated. Finally in 1884 the Grimmenthal-Ritschenhausen section and the 33 kilometre long section between Plaue and Suhl were completed. The building of this section included ramps with an average of grade of 2.0% and the 3,039 metre-long Brandleite Tunnel, which took just under four years to build and was very expensive. In August 1884 the first trains finally ran on the whole line.