The two designers, engineer Alexander Lindner and contractor Theo Bertschinger were supported by the mountain railway pioneer Roman Abt, who had responsibility for equipping the line with his newly developed Abt double lamella rack system.

However, the Brünig railway was not extended westward to Interlaken until 1916, so many early travelers to the Rothorn had to arrive by boat service on Lake Brienz.

The line was finally re-opened on 13 June 1931, the first train to reach the summit in 17 years having run four days earlier.

[4] The upper terminus of the line is at Rothorn Kulm station at 2,244 m (7,362 ft) above sea level, a little below the summit of the mountain.

[7] All steam locomotives are Class H2/3, indicating that two of the three axles are driven, giving a wheel arrangement (Whyte System) of 0-4-2.

The older locomotives are a side tank, "kneeling cow" design of a standard SLM product.

New Diesel locomotives were constructed by Ferdinand Steck Maschinenfabrik and are of (Whyte System) 0-4-0 wheel arrangement to a "kneeling cow" design.