Darjeeling Himalayan Railway built between 1879 and 1881, it is about 88 km (55 mi) long. It climbs from about 100 m (328 ft) above sea level at New Jalpaiguri to about 2,200 m (7,218 ft) at Darjeeling, using six zig zags and five loops to gain altitude.

Siliguri, at the base of the Himalayas, was connected with Calcutta (now Kolkata) by a metre gauge railway in 1878. Between Siliguri and Darjeeling, Tonga services ran on a cart road – the present-day Hill Cart Road.[3] Franklin Prestage, an agent of the Eastern Bengal Railway, approached the government with a proposal to lay a steam tramway from Siliguri to Darjeeling.[3] Ashley Eden, lieutenant governor of Bengal, formed a committee to assess the project's feasibility. The proposal was accepted in 1879 after a positive report by the committee,[3] and construction began that year.

A major difficulty faced by the DHR was the steepness of the terrain. Loops and zig-zags were incorporated along the route to achieve a comfortable gradient. When the train moves forward, reverses and then moves forward again (climbing a slope while doing so), it gains altitude along the side of the hill.