It was built to serve the ironworks at Länna with a connection to the 1,435 mm (4 ft 8+1⁄2 in) standard gauge railroad network.
The choice of gauge was somewhat of a compromise, 600 mm (1 ft 11+5⁄8 in) would have sufficed for the ore and steel traffic but with only a slight increase in budget allowed the greater capacity to carry passengers, mail and other goods.
In 1909, the company's name was changed to Stockholm–Roslagens Järnvägar (Stockholm-Roslagens Railroad), which enabled it to keep its signature (SRJ); Roslagen is the historical name of the coastal district north of Stockholm.
During the early 1950s, all three freight only branch lines to DHJ (to Lövstabruk, Ramhäll and Fagervik by Lake Vällen) were closed.
The latter was a city line with regular tram tracks, and for this reason freight trains never ran there, and steam engines only rarely.
That line was initially built with standard gauge, but was converted in 1934 to narrow-gauge, 891 mm, for practical reasons.
The SRJmf society was formed in 1968 with the main purpose of saving rolling stock from the SRJ/DHJ network for excursion traffic.
With the aid of the Municipality of Uppsala, traffic started on Sundays in the summer of 1974 when freight trains did not run.
The society could then take over the line Uppsala-Länna-Faringe, with the City of Uppsala as owner of the track and with the former junction Faringe serving as the headquarters with workshop facilities.