After the line has left the
Innerrhoden capital of
Appenzell—which is also served by the trains of the
Gossau–Wasserauen railway of the original Appenzell Railway—it runs over the
Sitter Viaduct to the Hirschberg loop, which offers views of Appenzell and the
Alpstein. Running next to the road, after passing over a watershed, the railway reaches the crossing station of Sammelplatz and, after about three kilometres of down grade, the entrance of the
Ausserrhoden village of
Gais. The line, which is now running away from the road, takes a tight 180° curve into the station of , where the trains that run over the
Stoss Pass to Altstätten wait, and the depot and workshop buildings of the former SGA are located. At the village exit, the line returns to the edge of the canton road again. On the following downslope are the stops of j and . Before the village of
Bühler, the line changes to the left side of the street. The line crosses the cantonal road again on the way to station. After the Goldibach bridge and a short climb, the line reaches the village of
Teufen at the hotel "Linde". The
station building, built in 1909, houses, along with retail outlets, tenants such as the
cantonal police. The line passes through the stops of , , and before reaching the St. Gallen quarter of Riethüsli. Until 2018, train crossings took place at the Liebegg
crossing loop south of
Riethüsli halt. Since 2018, the line has run through the Ruckhalde Tunnel on a decline of 8.0%, losing about in altitude, to the level of the once important SBB freight yard in St. Gallen. The tunnel replaced the last remaining rack section, which had impressive view of the western parts of the city, and the sharp Ruckhalde curve. The tunnel also made an approximately -long section of overhead line that had been shared with the
St. Gallen Trolleybus superfluous. Due to the lower voltage of the trolleybus network, the two forms of transport were electrically isolated from each other. The section with an S-curve leading to St. Leonhard bridge will be replaced by a new double-track section next to the SBB
St. Gallen–Winterthur railway by the end of 2021. After passing under the St. Leonhard bridge the line reaches the so-called St. Gallen
Nebenbahnhof (
"side station"), where a connecting building provides covered access to the standard-gauge trains of the SBB, its subsidiary
Thurbo, and
SOB. The inner city section which has an overhead line voltage of only 600 volts instead of 1500 volts starts in the and the cross-city line runs up to the (Brühl gate) parallel to the
St. Gallen Trolleybus line of the (, VBSG). This section is supplied by a common
traction substation. Originally, the trains to Trogen ran in the city on the tracks of the St. Gallen Tramway, which was closed in 1957, but this rail infrastructure now belongs to the Appenzell Railway. After taking over the tram infrastructure from the city of St. Gallen in 1959, the Trogen Railway was required to remove the second track in Bahnhofstrasse (between the station forecourt and the Schibener Gate — ). The second track in Bahnhofstrasse was not restored until 1978. The cross-city line is built as a
tramway to the road junction beyond Brühl Gate. It runs up to
Schülerhaus station on a double-lane track in the right-hand traffic and on
grooved rails on the surface of the street. The light-rail vehicles are equipped with turning signals and with a bell, in addition to the normal train whistle. Later, the line follows the St. Gallen–Speicher–Trogen cantonal road. From Schülerhaus, it has its own track with normal
flat bottomed rail. In this section, the line has the character of an
interurban, with trains passing on the left at the crossings loops, as in usual on
Swiss railways, unlike trams. Originally, the track was consistently built on the road on this section. From 1953, the track was moved to its own route with assistance provided under the (Private Railway Assistance Act), later the (Railway Act). The last part in the village of
Speicher, including the
station, was not moved from the road until 1997. The steep section between Schülerhaus and
Notkersegg offers a good view of the city of St. Gallen. Passengers can see the
Wenigerweiher (a former millpond) at the crossing loop and
Lake Constance after the former halt of Rankv (until 2018). Shortly after the high point of the line at the monument to the Battle of (part of the
Appenzell Wars) the line changes from the left to the right side of the road and reaches halt and then
Speicher station, where the depot and workshop of the former Trogen Railway are located. After halt, the line and the cantonal road cross the Sägibach, a tributary of the Goldach, and after passing through the halt of , it reaches its
terminus in
Trogen, formerly the location of a cantonal assembly (
Landsgemeinde). == Operations==