The Telemark power-based industry started in 1902 when Sam Eyde, along with Norwegian and Swedish investors, bought Rjukan Falls—establishing A/S Rjukanfos on 30 April 1903.

[1] The test plant in Notodden started operation on 2 May 1905 as the first in the world to produce synthetic potassium nitrate.

On 2 December 1905 Norsk Hydro-Elektrisk Kvælstofaktieselskab (now Norsk Hydro) was founded, and plans to start a new plant in Rjukan were initialized; moving closer to the source of power would improve efficiency and not make it possible for the newly independent Government of Norway to hinder construction of hydroelectric power by foreign investors—a major political issue at the time.

Rjukanfos applied for permission to build a power line from Rjukan to Notodden, but on 18 June 1907 the Norwegian Parliament did not accept the application, despite an offer from Eyde that the state would receive escheat after eighty years, in part because the state would have to guarantee 18 million kr for the project.

At the time it was common that lines built primarily for single-company freight transport would involve the subsidized operation of passenger and general cargo trains, at the expense of the railway owner.

Heavy local protests were transmitted to parliament in 1906, but by the next year an agreement was made for the construction of a general purpose line.

On 13 April 1907 Norsk Hydro and the German group Badische Anilin- und Soda-Fabrik (today BASF) made an agreement for the creation of the factory at Rjukan, Rjukan Salpeterfabrik, and at the same time created Norsk Transportaktieselskap—both companies were owned as 50/50 joint ventures.

Prostitution and the sale of illegal liquor during the prohibition flourished; the lack of proper law enforcement making Vestfjorddalen known as a lawless valley.

Negotiations were conducted in August, but failed—not until Minister of Labour Nils Claus Ihlen meddled and Sam Eyde pulled Norsk Hydro out of NAF and reduced his demands did the strike end, on 6 October.

[8] In 1907 the first ferry, an unmotorized barge named Tinnsjø was completed; the steam ship Skarsfos was used to haul it between the two railways.

She got a major overhaul in 1915 after the sister ship SF Hydro at 494 gross register tons was launched the same year.

The 1920 were a tough time, and cargo decreased, but in 1929 the electric arc technology was replaced by the ammonia method, with the main product being potassium nitrate.

The two kilometers (one mile) commuter train from Rjukan to Ingofsland took five minutes; a month pass cost NOK 2.50 for employees and their families.

During the 1930s NSB and Norsk Hydro initiated an attempt to attract tourists to Rjukan, through discounted direct trains from Oslo, Drammen and Skien.

[12] The German occupation of Norway (1940–1945) during World War II made the Rjukan Line the area for a massive struggle in between the Norwegian resistance movement and the Third Reich.

[13] One of the by-products at Rjukan was the production of heavy water—a key component in nuclear reactors, and necessary for the Germany designs as a moderator.

In early 1940, the entire stock of 185 kg was shipped to Paris, loaned to the French nuclear physics program at the College de France.

[14] The first attempt from the resistance was Operation Grouse in October 1942, but failed and caught by the Germans; as a consequence passenger transport after 7 April 1942 from Ingolfsland Station to Rjukan was only permitted for soldiers, police, workers at the plant and schoolchildren.

The resistance movement was aware of this plan, and considered blowing up the train at various places, but instead chose to target the ferry SF Hydro.

The attack was successful, the ship sank to 430 metres (1,410 ft) depth with 47 people on board, including eight German soldiers, a crew of seven and the cargo of heavy water.

[21] Norsk Hydro announced in 1963 a savings plan for its four plants in Norway; Chief Executive Officer Rolf Østbye made it clear that new technology in the production of ammonia would force the closure of the plant at Rjukan, and replace it with a petroleum-based process at Herøya.

[31] In 2006 the Norwegian Directorate for Cultural Heritage announced they would be working to preserve the railways and ferries,[32] and in 2008 it became clear that the directorate was working with an application for the Rjukan Line, the Tinnoset Line and the ferries to be included in a UNESCO World Heritage Site along with the closed plants in Rjukan and Odda.