On 30 August 1852, the government issued a decree outlining the initial route for what was then referred to as the "Caminho de Ferro do Norte" (Northern Railway).

The route planning north of Entroncamento began in 1856, with the section until Coimbra assigned to B. Wattier and the remaining to Francisco Sousa Brandão [pt] and John Rennie.

The final connection between Soure and Taveiro was completed in July 1864, enabling continuous rail travel between Lisbon and Vila Nova de Gaia.

In Aveiro, the alignment was adjusted to bring the line closer to the city, while the final approach to Porto involved significant challenges, particularly the crossing of the Douro River and navigating the rugged terrain near Vila Nova de Gaia.

The decision to bypass Tomar, motivated by the technical difficulties and higher costs of the proposed route through the city, caused considerable local discontent.

Similarly, the placement of Coimbra's station north of the city center, provoked debate over accessibility and urban planning.

[6] The project also involved extensive upgrades to nearby viaducts, tunnels, and support structures, alongside the modernization of tracks and technical equipment over a 3.8-kilometer stretch leading to Campanhã station.

In Espinho, an ambitious project reconfigured the rail line by constructing a 950-meter underground tunnel, relocating the station below ground and creating new urban connections.