On 17 September 1871, the Fréjus Tunnel was opened to traffic for the first time, facilitating a new era of interaction between France and Italy.

[1] Even with the arrival of new technologies such as the railway, the task of successfully traversing these peaks was viewed by numerous figures as a fool's errand, unfeasible to the point of being impossible.

However, there was a strong political desire amongst officials in both Italy and France to establish a railway between the two which, if completed, would launch a new era of transit and bring new commercial opportunities for both nations.

Considerable backing for the endeavor was forthcoming from individual Italians, not only in terms of funding, but also technical expertise, public endorsements, and labourers.

The tunnel took 14 years to construct, its rate of progress having been considerably increased via the use of new technical innovations such as pneumatic drilling machines powered by compressed air.

Ten drills were mounted in a frame to bore shot holes to receive blasting powder charges, with those in outermost positions aligned in a slight divergence from the centreline to increase the effective width.

Air at a pressure of 7 atm (710 kPa) was conducted in iron pipes from hydraulic compressors, powered by local streams at the mouths of the workings.

It was decided to redirect the tunnel to a new entrance positioned to the east of the original, where the ground was considerably more stable.

One specific and major alteration performed during this period was the enlargement of the bore to facilitate an equivalent loading gauge of French Lignes à grande vitesses (LGVs) throughout, thus enabling the tunnel to be traversed by wider rail vehicles, including container trucks on piggy-back wagons, as part of the Autoroute Ferroviaire Alpine.

[10] On 27 August 2023, a major landslide occurred on the line close to the tunnel at Saint-André à La Praz.

All traffic through the tunnel, including the major TGV and Frecciarossa services between the Gare de Lyon and Milan Centrale / Porta Garibaldi were suspended.