The 1,531 km (951 mi) railway line was opened to traffic in 1866 with the introduction of the "1 Down/2 Up Mail" train.

The 1,531 km (951 mi) long Howrah-Delhi main line (trunk route) has been divided in 6 sections: Railway transportation was introduced in India within 30 years of its maiden run in England.

The Governor General Lord Dalhousie foresaw a tremendous potential for the speedy means of transport in securing British control over a vast country, not only in moving goods and people but also in the movement of the armed forces.

The work included EIR's first tunnel at Jamalpur and first major bridge across the Son River at Arrah.

On 1 August 1864, coaches were ferried across the Yamuna at Allahabad to allow the first through train to travel from Kolkata to Delhi.

The Yamuna bridge at Allahabad opened on 15 August 1865 and in 1866 Kolkata and Delhi were directly linked.

On 6 December 1906, the Grand Chord line from Sitarampur to Mughalsarai via Gaya, which shortened further the Kolkata–New Delhi distance, was inaugurated by the Earl of Minto, the Viceroy and Governor-General of India.

[3] A pontoon bridge was built across the Hooghly River in 1874 to provide easy access to Howrah Station.

Some of the slower trains such as Toofan Express and Lal Quila, with more frequent stoppages, take around thirty hours.