When the Rigi Railway opened on May 21, 1871, it was the first rack railway in Europe. It first led from Vitznau on Lake Lucerne at an altitude of 439 m (1,440 ft) to the Rigi Staffelhöhe at 1,550 m (5,085 ft). Only two years later, after negotiations with the canton of Schwyz, could the route be extended to Rigi Kulm at an altitude of 1,752 m (5,748 ft). On this line, which has a gradient of up to 25 percent, the Riggenbach system is used, in which a single gear wheel engages the central rack from above.
The first ten locomotives were delivered between 1870 and 1873 by the workshops of the Swiss Central Railway in Olten and SLM. The four examples of the SLM were the first locomotives ever to be manufactured by this company. All locomotives were characterized by the fact that all equipment was inclined by twelve percent in order to enable easy water management in the boiler and convenient operation on the sections with different steepness.
In the beginning they had a vertical boiler, but this did not prove itself and was later exchanged for a horizontal one. The gear wheel was on the valley-side axle and was driven via a reduction gear. The cylinders were directly behind the axle on the mountain side. A centrifugal governor, which actuated the brake when the rotational speed was too high, protected the locomotive from excessively high speeds when going downhill. At the uphill end was an open baggage platform. One large or two small trailers could be taken along to transport people.
In 1899 and 1902, SLM delivered two heavier locomotives with horizontal boilers and a boiler pressure of twelve bars. These had a separate drive shaft, which was in the center of gravity of the locomotive and led to the relocation of the cylinders in front of the axle on the mountain side. They could now push a large and a small trailer at the same time.
Between 1911 and 1929 four of the locomotives were fitted with a superheater. The two older ones received a new boiler, larger cylinders and new piston valves. In the meantime number 14 appeared as H 1/2, which had come from the Arth-Rigi railway. Between 1913 and 1925 the three H 2/3 were put into service and the H 1/2 were soon used less often. With the electrification in 1937, all steam locomotives were retired. At this point, number 7 received the original vertical boiler again and has been operational again since 1996.
