[1] Its network was one of the most extensive in Spain, until it was nationalized in 1941, and integrated into the Red Nacional de los Ferrocarriles Españoles (RENFE).

[1] The origins of Norte lie on the construction of the Madrid-Hendaye railway, designed to link the Spanish capital with the French border.

The change in railway policy in 1851 obliged the Biscayans to adapt to the condition of payment on behalf of the State, by means of a second concession.

The first major difficulty that the line's engineers had to face was the Sierra de Guadarrama, which was solved with the completion of the Torrelodones tunnel.

[8] At the end of this period, with the economic recovery, many railway companies were in a difficult financial situation and unable to meet the accumulated debts.

In 1890 a branch line was built from Soto de Rey to the mining area of Langreo, to send its coal directly to Castile without passing through the port of Gijón.

On August 14, 1884, it acquired the Compañía del Ferrocarril de Lérida, Reus y Tarragona, which consolidated its position in the Catalan region.

The operation was intended to complete the previous acquisition of the railway lines in the Levant, but this failed because MZA went ahead and in 1891 managed to take over the TBF.

In this sense, the Puerto de Pajares line, with a sloping ramp along the entire route and 70 tunnels, was one of the hardest in Spain and for its transit several locomotives were almost always necessary.

[2] On July 24, 1918, the Minister of Public Works Francesc Cambó approved the electrification of the Pajares ramp, the objective of which was not to electrify the entire line, but only the 62-kilometer section between Uxo and Busdongo.

This system was until then used exclusively in the United States and in fact its first important application was for the Chicago, Milwaukee, St. Paul and Pacific Railroad (CMStP&P), between 1915 and 1917.

Although this system presented a much higher voltage than that which had been used in Europe until then, it offered the advantage of requiring fewer substations and a cheaper catenary.

The Norte company came to have a large number of workers on its payroll: factors, administrative staff, train drivers, stokers, operators, mechanics, etc.

For this reason, within the company, the workers' unions achieved a great influence and capacity for action, as was seen during the railway strike of July 1916.

[19] In September 1926 the Compañía del Ferrocarril Central de Aragón was acquired from the Belgian shareholders who controlled it,[20] after which it became a subsidiary of Norte.

[24] In view of the new situation, the Republican government seized all the railways in its area by decree of August 3, 1936,[25] although in practice control fell to the workers' and railwaymen's committees.

The Norte company had to face the destruction or serious damage to 56% of its stations —especially Madrid's Estación del Norte—; 27% of the bridges, viaducts and tunnels; as well as a large number of tracks and railway installations of various kinds.