In 1870, prompted by the then Colonial Treasurer Julius Vogel (1835-1899), the Government adopted bold, expansionist policies that would bring thousands of assisted immigrants to New Zealand to construct roads, railway, bridges and telegraph lines. Part of Vogel's vision was to create a railway line that would connect the country's two main cities, Auckland and Wellington.
Yet part of the North Island Central Plateau known as the King Country, or Rohe Potae, was one of the semi-autonomous Maori states that survived the New Zealand Wars of the 1860s. It was the heartland of the King Movement that prevented unauthorised Pakeha entry into the area for almost a decade after the wars, resisted the alienation of Maori land to Pakeha, and boycotted the Native Land Court. While this land remained part of the colony over which the government had 'no practical control', Vogel's vision would remain more of dream than a practical suggestion.
By 1880, existing railway lines had been extended in both the north and the south of the North Island. A railway had been opened from Foxton via Palmerston North, Marton, and Wanganui, to Waitotara in Taranaki, and in the Auckland district the line through Mercer had been extended into the Waikato as far as Te Awamutu on the border of the King Country. To achieve Vogel's vision, approximately 200 miles (circa 322 kilometres) of track would have to be constructed between Marton and Te Awamutu, to connect the lines that were in operation in 1882.
In 1882 the government enacted the North Island Main Trunk Railway Loan Act to enable the raising of the finance (£1,000,000) for closing the gap between the railheads and began negotiations with Ngati Maniapoto chiefs for permission to survey a route for the line through the Rohe Potae.
By the 1880s, Maori within the Rohe Potae had decided that a controlled opening was essential if they were to 'protect their lands from rival claims, participate in new economic activities, and to ensure their future prosperity'. However, the debate over how this could be achieved caused a split among followers of the King Movement. Some, including King Potatau Te Wherowhero Tawhaio (? - 1894), wanted an agreement with the Government that would ensure their continued authority and effective political voice in the area before allowing any developments such as railway surveys to go ahead. Others, including chiefs such as Rewi Manga Maniapoto (? - 1894) and Wahanui Huatare (? -1897), perceived benefits in using the Native Land Court to confirm title to land they wished to lease, and allowing public works development in the area.
Maori who perecieved benefits in the Native Land Court system entered into negotiations with the government and a series of agreements, collectively known as the Ngati Maniapoto 'compact' or 'Aotea agreement' were entered into. For iwi, the purpose of these agreements was to secure a legally recognised boundary around the Rohe, and provide a means by which they could determine land titles within that boundary. For the government, the compact was to secure the right to survey a route for the NIMT through the area.
In June 1883, Maori presented a petition to parliament that asserted Maori rights to exclusive and undisturbed possession of iwi lands but indicated a willingness both to consider leasing and to allow a survey of the route for the NIMT. Tawhiao, who strongly disapproved of the document, sent a counter-petition, which was ignored. To demonstrate their faith in the agreements made, Maori allowed the survey to go ahead. Cathy Marr notes that the government apparently regarded the agreement as 'simply one to allow the railway surveys to begin and did not feel obliged to meet the requests outlined in the 1883 petition'. Marr further notes that it appears that Maori, who expected to receive considerable benefits from the construction of the railway, were never in fact paid compensation for the land taken to construct it.
In June 1883, surveyor and engineer John Rochfort (1832-1893) set out to inspect the territory through which the proposed line would be laid. During his journeys, Rochfort met with strong resistance from Maori opposed to the construction of the line, and for three days was held prisoner at Papatupu, near Ohakune. Despite this, Rochfort's work enabled the House of Representatives to settle on the 'the central route from Marton to Te Awamutu as the best for the North Island Main Trunk Railway'.
On 15 April 1885, a ceremony for the turning of the first sod on the new line was held near Puniu, 2 miles (3.2 kilometres) south of the northern railhead at Te Awamutu. Premier Robert (later Sir Robert) Stout (1844-1930), Rewi Manga Maniapoto, and Wahanui Huatare, attended the ceremony.
By 1887, despite hindrances caused by the difficult terrain and reduced government funding, the line had been opened to Te Kuiti, 42 kilometres south of Te Awamutu and, at the southern end, 30 kilometres of track had been laid. This left the most difficult section of the line, from north of Hunterville to south of Te Kuiti. This section required the construction of major viaducts across the Makohine and Mangateweka streams, and the Makatote River. Although John Rochfort had surveyed much of the proposed route, difficult decisions about alignment remained; it was civil engineer Robert West Holmes (1856-1936) devised the seven mile (circa 11.26 kilometre) spiral configuration that resolved the problem of how to lose 715 feet (circa 217.93 metres) of height without breaking the gradient of 1 in 50 when bringing the track out onto the Waimarino plateau from the south.
By 1906, the line had reached Turangarere in the south, and Raurimu in the north. The then Minister of Public Works William Hall-Jones (1851-1936) almost doubled the workforce of 1300 men, employing 600 extra men to complete the Spiral, the remaining viaducts, and the track. Housed in makeshift camps, and supplied with picks and shovels, these men carved out the route of the line through the dense native bush, and mountainous terrain that covered much of the central plateau. The last viaduct was finished on 10 July 1908, and on 3 August the two railheads met at Manganui-o-te-ao. Five days later the first train travelled the entire length of the route between Wellington and Auckland. Despite this, the line remained makeshift in a number of areas and work continued into the following year.
On 6 November 1908, 38 years after it was first proposed by Vogel, the NIMT was officially completed. During the celebratory ceremony, the then Prime Minister Sir Joseph Ward (1856-1930) drove a silver-plated spike, the official last spike of the railway line, symbolising the completion of the project and the connection of Wellington with Auckland by rail. In fact, the actual last spike was driven 300 metres south of the spot where the two railheads met as, during the ceremony, rails were still being laid across the Manuganui-o-te-Ao viaduct. Regular passenger services between Auckland and Wellington commenced on 15 February 1909.
The silver spike has long since been 'lost', but a further acknowledgement of the enormous achievement of all those involved in the completion of the NIMT was later made when a concrete obelisk was erected near the roadside at Manganui-o-te-ao. It is unclear when the obelisk was erected. The obelisk is inscribed with the name of William Hall-Jones (1851-1936), who is described as the Minister for Public Works and Railways. Hall-Jones was Minister for Public Works between 1896 and 1908, and Minister for Railways between 1906 and 1908. This suggests that the memorial was erected shortly after the official completion of the NIMT in 1908. However, the first-known picture of the structure dates from 1921. It was moved thirty feet in 1973 to the west side of the track.
In 1997 a ceremony was held to acknowledge the importance of the engineering and construction skills of those involved in the project, and to acknowledge the importance, at that time and ever since, of the connection of the two major cities of New Zealand. The Institution of Professional Engineers New Zealand and the prestigious American Society of Civil Engineers then upgraded the signage on the obelisk and designated the site an International Historic Civil Engineering Landmark.