Split and merged
When the Government decided to establish a main line railway network in 1855, Nils Ericson was appointed director of the single-person authority Statens järnvägsbyggnader until 1862. When he eventually stepped down, the authority was split into two parts.
One part – Styrelsen för statens järnvägsbyggnader (SJB) – was responsible for construction, while the other – Styrelsen för statens järnvägstrafik (SJT) – was responsible for traffic services. SJT used the name Statens Järnvägar as its brand from the outset. In 1888, the authorities were merged into a new government authority – Kungliga järnvägsstyrelsen.
SJB was part of this new authority up until 1938, when the railway in Sweden was completed and SJB was shut down. Kungliga järnvägsstyrelsen existed until 1963, at which time SJ underwent fundamental reorganisation.