The need for a rail connection between the (upper) Lahn valley and the Ruhr was first identified by Splingard, chief engineer of the then Electorate of Hesse, in 1847.

[2] The cost of the entire line from Marburg to Cologne via Biedenkopf and Siegen, including branch lines to coal mines, was estimated at around 28 million guilders, but only slightly less than 900,000 guilders had to be raised for the section between Kreuztal and Cölbe, since there was little requirement for expensive tunnels, embankments and other structures.

In particular, it would supply the numerous hammer mills, smelters and foundries along the line and in the hinterland with coal and coke from the Ruhr area for the blast furnaces and cupola furnaces (wood for charcoal having become scarce) and enable iron and steel products to be transported back to the Ruhr at competitive prices.

The trains, made up of two Silberling coaches and a class 211 locomotive, were virtually only used for trips to and from work and school.

In 1994, the rail buses and locomotive-hauled trains of coaches between Siegen and Bad Berleburg were replaced by class 628 multiple units.

The local line, which was advertised as the "Rothaar-Express" when it was launched, has run hourly between Bad Berleburg and Siegen since then.

In recent years, the Kurhessenbahn has paved the platforms at all stations (except Wallau) between Marburg and Bad Laasphe and raised them to a height of 38 or 55 centimetres.

The modernisation included the track infrastructure, the upgrade of the platforms to allow barrier-free movement and the construction of an electronic interlocking.

Deutsche Bahn, the federal government and the state of North Rhine-Westphalia invested a total of €13.8 million in the modernisation.

In order to enable a connection for freight to the south of the line, however, a new level crossing had to be established.

[13] In Kreuztal-Ferndorf there are still two industrial sidings (to Bender Eisen- und Metallwerke Ferndorf and for galvanised steel from Thyssen Krupp Stahl AG) with considerable freight traffic.

In Dahlbruch, three sidings are regularly served by DB Cargo (Eisenbau Krämer, SMS and a scrap dealer).

[15] The transport services of the "Nordwesthessen" (northwest Hesse) diesel network were awarded to the Kurhessenbahn for a further 15 years with the start of the contract in December 2017.

Originally, passenger services were to be re-awarded as early as December 2015, so a two-year bridging contract with the Kurhessenbahn was necessary.

In addition, an hourly service was introduced with the start of operations on the RB 94 on Saturdays between Bad Laasphe and Marburg.