Over the next three years, the line between Dunedin and Christchurch was constructed; Christchurch and Timaru were linked on 4 February 1876, followed by Oamaru on a year later, and the difficult section between Oamaru and Dunedin was finally completed on 7 September 1878. All that remained was the Balclutha-Gore link, which was opened on 22 January 1879, completing the Main South Line. Main North Line Construction of the Main North Line was one of the longest construction projects in New Zealand's history. Through the 1870s, work on a line from Christchurch to northern centres in Canterbury was undertaken, with a line through Kaiapoi, Rangiora, and Amberley reaching Waipara in 1880, and at the other end, a line linking Blenheim and Picton opened in 1875. Further construction was delayed by disputes over proposed routes. Different regions sought to protect their interests by having the line constructed through their area. Some preferred the coastal route via Parnassus and Kaikoura, while others favoured an inland route to Blenheim with a branch from Tophouse to Nelson. There was also a proposal to use the latter route as the trans-Alpine line (as the Midland Line's route was yet to be chosen), linking Waipara with Reefton and then connecting to Nelson and possibly Blenheim via a line up the Buller Gorge. The people of Marlborough favoured a coastal route and began work south, while in Canterbury, work initially began on an inland route, with Waipara linked to Culverden in 1886. Although the line to Culverden was treated as the mainline for decades, it eventually became part of the Waiau Branch. At the start of the 20th century, work began on a coastal route northwards from Waipara, with the line opened to Parnassus in 1912. Construction then proceeded up the Leader River valley as part of a somewhat inland route to Kaikoura via river valleys, but the start of World War I brought a halt to construction and the 3 km of track laid beyond Parnassus was removed. The war also brought a halt to work at the northern end, with the coastal village of Wharanui established as the terminus of the line south from Blenheim. The 1920s saw much indecisiveness and disputes over what route to take between Waipara and Wharanui. The Culverden line now ran all the way as Waiau and some work took place on a line to link Waiau with Kaikoura, but