The tunnel was built as part of a deviation to replace the costly Rimutaka Incline and its Fell engines.

One promising possibility was a 5-mile (8.0 km) tunnel between Mangaroa and Cross Creek, which received so much attention that it nearly became the much-sought deviation.

The contract was expected to be completed in four years, but the headings met on 20 April 1954 with the concrete lining finished a month later.

The tunnel was partly built using full face operation rather than the traditional heading and bench excavation.

Most were single men and lived in huts at camps or a bunkhouse at the Mangaroa or Featherston portals, which had cookhouses and mess halls plus 20 houses each for married staff.

[4] New Zealand Railways took possession of the tunnel on 1 February 1955, which also included approach formations and bridge piers, at which time track laying commenced.

On 3 November 1955, the new line was opened and two special trains travelled from Wellington to Speedy's Crossing to the inauguration ceremony.

[9] After its completion, a 2.74 metres (9.0 feet) diameter vertical ventilation shaft was driven up from a point almost halfway through the tunnel.

[11] The Maoribank Tunnel is 555 metres (1,821 ft) long; it was tendered separately in 1953 and constructed by MKD, work started in October 1953 and was completed in December 1954.

[15] As a health and safety measure, staff on trains travelling through the tunnel carry gas detectors to detect the buildup of noxious gases.

[16] There have been proposals to electrify the tunnel and the Wairarapa line as far north as Masterton as an extension of the Wellington suburban electrification.

From 2014 diesel locomotives hauling passenger trains in long tunnels were required to have fire suppression equipment, following the Pike River Mine disaster inquiry.

[20] The tunnel is used for freight from the Wairarapa to Wellington, notably logs from local pine forests and wood products from the Juken New Zealand Ltd timber mill at Waingawa, just south of Masterton.