Despite running under the Fréjus Pass, it is sometimes called the Mont Cenis Railway because, from antiquity until the Fréjus Rail Tunnel was opened in 1871, most people used the Mont Cenis Pass to get between France and Italy.

[4] The remaining section between Saint-Michel and Modane and the tunnel towards Italy were opened on 16 October 1871.

The 20-kilometre-long (12 mi) section between St. Michel to Modane on the north side of the Mont Cenis Tunnel has a maximum inclination (gradient) of 3%, an average inclination of 2.1% and a smallest curvature radius of 350 metres (1,150 ft).

The erection of support structures in difficult areas with danger from landslides, and of tunnels with a total length of 4,624 metres (15,171 ft) was necessary.

On this section 18 bridges and 26 tunnels with a total length of 8,115 metres (26,624 ft) were built.