After two more kilometers, the border between the cantons of Uri and Ticino is passed; after another five kilometres (3 mi), the tunnel ends at the southern portal near to Airolo (1,142 m or 3,747 ft).

[3] Even prior to the scheme's commencement, such a tunnel had been envisioned as a necessary but singular element of a wider railway network that would connect the North Sea and the Mediterranean Sea together, opening up new commercial opportunities by facilitating the movement of goods and people between the ports of Belgium, the Netherlands, and Germany with those of Northern Italy, along with many of the major inland cities lying in between.

[3] It was decided that the contract to build the tunnel ought to be subject to a competitive tendering process, during which a bidding war broke out between two engineering companies, based in Geneva and Italy respectively.

As a consequence of the relatively low bid, which contrasted poorly against the additional costs that were incurred during construction, Favre increasingly found himself at odds with Swiss politicians and investors alike.

[6] Even prior to the onset of construction activity, the location of the tunnel presented challenges that exceeded those of the earlier Fréjus Rail Tunnel; due to both the steepness and height of the summits, surveys using direct observation were impossible, thus more complex indirect techniques combining triangulation and accurate cartography were performed by a team headed by M. Gelpke, and subsequently confirmed by a second team led by M. Koppe via different methodology.

Another key innovation was the use of mechanised tunneling machines, which Favre, supervisor of the work as well as prime contractor, strongly advocated for, despite pressure to make greater use of manual boring.

[10] During 1875, the workforce went on strike; this was promptly violently suppressed by local police force (21 men) from Altdorf, resulting in four deaths amongst the workers and the wounding of 13 others.

[3] It was also observed that a high degree of accuracy had successfully been achieved, a testament to the stringent surveying and directing that had been performed throughout the construction phase.

These finishing works were considered to be relatively low risk compared with the preceding boring that had taken so long, and was actually easier to complete than the approach lines to meet with either end of the tunnel.

The opening drew substantial international attention; the president of Switzerland, Simeon Bavier, praised the project and declare it to be: "A triumph of art and science, a monument to work and diligence!

[12] Initially, the tunnel was operated by the private railway company Gotthardbahn, which ran conventional trains drawn by steam locomotives between Lucerne and Chiasso at the Italian border.

There were also some concerns over the tunnel's ventilation being sufficient considering the challenging conditions encountered during construction, but it was believed that these would settle during routine operations without the need for extensive intervention.

Initially, the voltage had to be reduced from the desired 15 kilovolts to 7.5 kV, because the grime deposited on the insulators by the steam locomotives encouraged excessive arcing.

Today, that service exists as the rolling highway from the German to the Italian border and aims to reduce truck traffic on Swiss expressways.

An improvisational piggyback service from Göschenen to Airolo was offered during the two-month closure of the Gotthard Road Tunnel following a fatal fire caused by a collision in 2001.