The line was built to exploit iron ore which had been discovered by Nils Persson and later sold to Edison Ore-Milling Company.

After the war, the Norwegian State Railways had to carry out extensive upgrades to the line for it to meet modern standards.

The Dunderland Line was a single track, standard gauge 23.7 km (14.7 mi) railway between Gullsmedvik and Storforshei.

[1] It started at Mo i Rana Port at Gullsmedvik and ran up the Dunderland Valley until it reached Rena Mine at Storforshei, following the south shore of the river Ranaelva.

[2] The line starts at Gullsmedvik, which is currently located 500.85 km (311.21 mi) from Oslo Central Station.

[5] Ole Tobias Olsen discovered iron ore on his farm of Nord-Dunderland, for which he registered a mining claim in 1879.

[7] In 1891, he petitioned the government to look at his claim as a source of national wealth and requested that the Nordland Line be built via the Dunderland Valley to allow shipment of the ore to the coastal port of Mo.

[6] A Swedish investor took initiative to build a line up the Dunderland Valley as a private railway.

[6] During the 1880s, Swedish industrialist Nils Persson and his engineer Alfred Hasselbom found large deposits of ore in the Dunderland Valley.

British investors bought DIOC in 1938, but because of the ore's high phosphorus content, only German mills were interested in purchasing the ore. After Germany declared war on the United Kingdom on 3 September 1939, production was halted.

[11] With the German occupation of Norway during the Second World War, construction of the Nordland Line, which by then had reached Mosjøen, became subordinate to the Wehrmacht.

On 12 April 1943, traffic opened on the section between Mo i Rana to Nevernes, consisting of 3 km (1.9 mi) from Mo to Tverånes, the Dunderland Line from Tverånes to Bjørnhei and the 4.4 km (2.7 mi) section from Bjørnhei to Nevernes.

The construction work on the Nordland Line was of poor quality, resulting in low operating speeds.