This happened from the mid 1800s towards the late 1800s.
Davos, one of the towns in Grisons, during that same time period had acquired a reputation for a healing climate for lung ailments, especially tuberculosis.
In order to make the journey from Landquart - which the standard gauge railway had already reached - less exhausting and time consuming a railway was proposed.
The driving force behind the project was a recent arrival to Davos.
Willem Jan Holsboer - a Dutchman who's wife suffered from a lung ailment - had brought her to Davos and was the founder of the first treatment facility.
He quickly realised that different transportation was required in order to make Davos more accessible. The proposal of a railway line was the next step.
With his influence in both financial circles as well as with the people of the Prättigau Valley he managed within a short time that construction could proceed in the Spring of 1888.
Due to the topography and the reduced costs it was decided to build the railway as a narrow gauge line using 1m for track gauge.
The first section of the line was inaugurated on Oct. 9th 1889. The line had reached the town of Klosters.
Less than a year later, on July 21st 1890 trains would start running to Davos.