The first lap was a 184.9 kilometres (114.9 mi) long journey along the Eastern Bengal State Railway from Calcutta Station (later renamed Sealdah) to Damookdeah Ghat on the southern bank of the Padma River.

The second lap of the journey was a 363.1 kilometres (225.6 mi) metre-gauge line of the North Bengal Railway that linked Saraghat on the northern bank of the Padma to Siliguri.

[3] In 1916 the metre-gauge section north of the bridge was converted to broad gauge, and so the entire Calcutta – Siliguri route became broad-gauge.

[4][5] With the partition of India in 1947, the major hurdle in connecting Kolkata and Siliguri was that there was no bridge across the Ganges in West Bengal or Bihar.

The rail bridge was thrown open to the public in 1971, thereby linking the Barharwa–Azimganj–Katwa loop to Malda Town, Barsoi, Kishanganj, New Jalpaiguri and other railway stations in North Bengal.