On 6 August 1846 the body responsible for building the line was named the Elector Frederick William Northern Railway Corporation (Kurfürst-Friedrich-Wilhelms-Nordbahn Aktiengesellschaft).

The states of Saxe-Weimar-Eisenach, Saxe-Coburg and Gotha, Prussia and Kurhessen began negotiations in 1840 on the establishment of an east–west rail link between Westphalia and Halle.

The main line would run between Kassel and Bebra through Kurhessen from Gerstungen in the east to Haueda, 14 kilometres west of Hümme on the border with Westphalia.

Negotiations were completed in the autumn of 1841 and in 1844 the Elector Frederick William Northern Railway Corporation received the concession to construct the line.

The branch line to Carlshafen opened on 30 March 1848 at the same time as the 11.5 kilometre section of the Gerstungen–Kassel–Haueda main railway between Hümme and Grebenstein.

Its major structures were the 202 metre-long Deisel Tunnel between Trendelburg and Wülmersen that passed through the Kesselberg mountain, thus avoiding the Diemel valley flood plain, and a triple-arched viaduct over the Holzape, one of the streams that starts in the Reinhardswald.

In parallel, river traffic on the upper Weser, which was strongly affected by changes in water levels, was significantly impacted by the opening of the Hanoverian Southern Railway in 1856 from Göttingen via Hann.

The company was renamed the Hessian Northern Railway (Hessische Nordbahn) and it planned to build a line from Karlshafen via Detmold and Herford to Lemförde.

Although the BME planned several variations of an eastward extension of Carl's Railway between 1873 and 1878, these always failed due to lack of funds.

The Reichsbahn attempted to economise by closing Stammen and Wülmersen stations, or at least reduce the number of trains stopping there, which led to widespread protests.

Around 1950, the extension of the Carl's Railway to connect with the Northeim–Ottbergen–Altenbeken line was again discussed; this would have required the construction of an approximately 530 metre-long tunnel.

The unfavourable topographical conditions in Karlshafen created difficulties, however, and it was decided to cater for the north–south long-distance freight traffic on the Warburg–Altenbeken route by construction a bypass curve at Altenbeken station to the Hamm–Warburg line.

Freight on the Carl's Railway at this time was limited and was handled by a class Köf II shunting locomotive to/from Hümme station.

Railway sidings existed in Karlshafen (Weserhafen), in Wülmersen (estate) and Trendelburg (sand quarries).

On 25 September 1966, the last passenger service ran on the Carl's Railway and freight operations closed on the eleven kilometre-long Trendelburg–Karlshafen section.