In the pre-partition days, Assam was linked to Chittagong through the Akhaura-Kulaura-Chhatak Line and Akhaura-Laksam-Chittagong Line. The Chittagong link had been constructed in response to the demand of the Assam tea planters for a railway link to Chittagong port. Assam Bengal Railway started construction of a railway track on the eastern side of Bengal in 1891. A 150-kilometre long (93 mi) track between Chittagong and Comilla was opened to traffic in 1895. The Comilla-Akhaura-Kalaura-Badarpur section was opened in 1896–1898 and finally extended to Lumding in 1903. The Assam Bengal Railway constructed a branch line to Guwahati, connecting the city to the eastern line in 1900. During the 1900–1910 period, the Eastern Bengal Railway built the Golakganj-Amingaon branch line, thus connecting the western bank of the Brahmaputra to the western line.
The railway tracks from Guwahati to Lumding and from Chaparmukh to Haibargaon were upgraded from metre gauge to broad gauge in 1994.
The Guwahati-Lumding-Dibrigarh line was proposed to be doubled in the Railway Budget for 2011-12.
The 44.92 km (28 mi) long Lumding-Hojai doubling project was sanctioned in 2012-13. The 30.50 km (19 mi) long New Guwahati-Digaru doubling project was completed in 2012-13.
The Assam Railway and Trading Company Limited was merged with Assam Bengal Railway in 1945. With partition, Assam Bengal Railway was split up and railway lines in Assam became Assam Railway. In 1952, North East Railway was formed with the amalgamation of Assam Railway, Oudh-Tiirhut Railway and the Kanpur-Achnera section of Bombay, Baroda and Central India Railway. Northeast Frontier Railway was created with a part of NE Railway in 1958.