Built by Robert Stephenson, the Trunk Line was opened on 1 September 1854 by the Norwegian Trunk Railway (Norwegian: Norsk Hoved-Jernbane), making it the oldest public railway line in Norway.

It connected to steamboats on Lake Mjøsa, allowing steam powered transport to places like Lillehammer, 180 kilometers (110 mi) from Oslo.

The section between Kristiania East and Lillestrøm was rebuilt to double track in 1902, and the line was electrified in two portions, in 1927 and 1953.

In addition overcrowded trains are not allowed through the Romerike Tunnel, and are occasionally diverted to the old line.

[1] Passenger service on the old line past Jessheim is only provided to Dal.