The Bodensee–Toggenburg railway is a mainly single-track standard-gauge line connecting Romanshorn on Lake Constance (Bodensee in German) and the Toggenburg region in Eastern Switzerland.

The first railway lines in Eastern Switzerland followed the river valleys and thus resulted in some large detours to the east for travel to the canton capital of St. Gallen.

The first expert opinion recommended a gap between Ebnat and Uznach, but this would still have required a detour via Wil to reach St. Gallen.

The leader was the Degersheim embroidery manufacturer Isidor Grauer-Frey, who also campaigned for an extension of the line beyond Rapperswil to Zug in order to make a connection to the Gotthard Railway.

In 1889, the Grand Council granted the initiative committee a contribution of CHF 5,000 to submit an application for a concession for a St. Gallen–Zug railway.

Grauer-Frey's vision of a continuation of the line from Rapperswil to Zug remained unfulfilled and the concession expired after the Federal Assembly rejected a further extension of time on 22 December 1906.

Nearly 90 years later, this dream re-emerged for a short time with a proposal for a "Hirzel Tunnel" under the New Railway Link through the Alps project.

In contrast, the St. Gallen–Romanshorn and the Ebnat–Nesslau Neu St. Johann projects, which were promoted by other initiators, were combined with the St. Gallen–Wattwil line into a single concession (Federal Decrees of 19 December 1902 and 11 April 1907).

[2] The St. Gallen municipal council however, wanted a standard gauge railway to the port of Romanshorn, which served the Lake Constance train ferries.

At that time, Romanshorn was an important hub for freight traffic between Switzerland and Germany because the Basel Rhine ports did not start operating until 1922.

The new Swiss Federal Railways (SBB) began the construction of the Ricken Tunnel between Wattwil and Kaltbrunn on 17 November 1903.

The BT had to contend with countless difficulties in its construction, so that the opening, which had been planned for the spring of 1910, had to be postponed for half a year.

Mogelsberg and Brunnadern received stations modelled on a Toggenburg farm house (a variety of Swiss chalet) with a timber-frame extension.

The stations buildings of Roggwil-Berg and Neukirch-Egnach show similarities with the country houses that the wealthy of St. Galler and Konstanz built in the 18th century.

The BT had procured its own rolling stock, but entered a contract with the SBB for its operation, because it hoped for financial savings as a result.

With a 6.5% grade and curves with a minimum radius of 60 to 70 metres, the western end of the line would not have caused much difficulty.

Since the concept of "light operation" proved to be successful, not only locomotives, but also railcars were procured for the electrification of the line.

The fact that they were not kept as a reserve for independent operations over unelectrified lines, such as the diesel railcar of the Appenzeller Bahn, suggests that their petrol engines were not completely satisfactory.

From a technical point of view, there was still a great deal of uncertainty and no cost savings compared to steam operation.

On 18 October 1920, BT's board of directors decided to electrify the St. Gallen–Wattwil–Nesslau line, but it rescinded this decision a year later, after coal prices had quickly returned to normal.

The Confederation and the cantons (with the involvement of the municipalities) granted the BT an electrification loan of CHF 3.9 million.

Thus the Direkte Linie Nordostschweiz–Zentralschweiz (north-east Switzerland–central Switzerland direct line) was created, which is now marketed as the Voralpen Express.

In the 1930s, the financial situation deteriorated so much that a partial renovation of the line was necessary in 1942/43 at the expense of the Federation and the cantons of St. Gallen and Thurgau.

It was not until a new Railways Act was passed by the federal government in 1958 that the way was clear for the comprehensive renewal of the infrastructure and rolling stock fleet.

This train was equipped with fluorescent tube lighting, rubber-covered gangway connections and a built-in end-of-train device.

With its first investment program, the rolling stock fleet was expanded in 1966–68 with three other BDe 4/4 push–pull trains and twelve Einheitswagen I (Swiss "unity coach 1", built between 1956 and 1967) and the mechanical signal boxes were replaced by relay interlockings.

The focus of the upgrade of the Wittenbach–St.Gallen–Herisau–Degersheim section in 1973–1982 was to create a modern suburban line with customer-friendly station facilities.

The first section of double track was opened in Gübsensee in 1989, allowing half-hourly services between St. Gallen and Wattwil.

Under new leadership and in a changed political environment in the 1990s, talks began again on closer cooperation between the BT and the SOB.

Bridges over 40 m long: Because the BT's line basically consisted only of sections with connections that belonged to the SBB, personnel and rolling stock were always deployed across company boundaries.