The railway in Sweden has its absolute greatest coverage in 1938 with 16,886 km. In 1939, the Riksdag (parliament) decides on the general nationalisation of the private railways (on a voluntary basis).

In 1939, 8,046 km are state railways (SJ plus the former nationalised railways) and 8,711 km private.

After the great wave of nationalization is over in 1949, 14,782 km are state-owned and 1,875 km are private. This largely creates a monopoly for SJ.