Badische Hauptbahn
The main reasons for planning such a line were: first, to create a route running north–south to Switzerland to rival the Baden Mainline between Mannheim and Basel, particularly since there was then no link between the Baden Station and the Central Station in Basel; and secondly, the section between Calw and Horb, together with the planned Württemberg Black Forest Railway between Stuttgart and Calw, was to make up a new north–south mainline to replace the Upper Neckar Railway opened in 1864. (A direct southwards connection from Stuttgart crossing the Gäu plateau was not initially undertaken because of the topographic problems).