This was due to the comparatively easier terrain faced by the route in the valley of the Grey River, and in 1889, the line was opened to Ngahere.

On 29 February 1892, the NZMRC opened the line all the way to the south bank of the Inangahua River, directly opposite Reefton, and with the Stillwater–Reefton portion complete in their view, they redirected their energy to the Midland route from Stillwater to Otira.

Work on the SWL recommenced in the 20th century, with the Inangahua River bridged, the present-day Reefton station established, and a further section to Cronadun opened in 1908.

[11] The Buller Gorge posed many difficulties for construction, but most of the formation and 2[12] of the remaining 12 bridges[13] had been built, when Parliament voted 40:22 on 8 October 1931 to back the Railways Board proposal to stop work on the Westport-Inangahua line as well.

[15] The outbreak of World War II created further delays on construction, but this time, work continued through wartime,[16] including electric signalling, a turntable at Westport and easing of grades at Omoto, Jacksons and Stillwater.

Labour MP, Bob Semple, called stopping the works and throwing wheelbarrows, tools, and shovels in the river, a criminal offence.

A 2017 report said the Stockton Mine is the main source of traffic and that, "if production were to drop significantly, the economic viability of the whole rail network west of Canterbury would be questionable.

This was the last mainline duty performed by the B and BA locomotives, and as bridges on the SWL were strengthened, they were displaced in the 1960s by the heavier A and AB classes.

One notable feature was the necessity to bank heavy trains heading south from Reefton to Stillwater due to the difficult uphill grade.

This was a common feature during the era of steam locomotives, and although banking was dispensed with on most lines when the conversion to diesel-electric motive power was made, the SWL was initially an exception.

With a 50 km/h (31 mph) maximum speed in the Gorge, due to curvature, there have been no serious injuries and 25 km/h (16 mph) limits are between Te Kuha and Cascade, at the worst spot, and below the limestone cliffs of Whitecliffs, where KiwiRail monitors metal pins across the limestone to check it remains stable,[37] just west of Buller.

[47] Stations and sidings on the southern section of the line (those north of Westport are listed in the Seddonville Branch article) – NB the opening and closing dates in columns 3 and 4 sometimes vary from those in the notes, which are derived from different sources.

[66] About 500 m (550 yd) south of the loop, in Mawhera Reserve, beside SH7,[80] is a geared 0-4-4-0 bush loco built by G & D Davidson in Hokitika in 1913, which worked on the Red Jacks Sawmilling Co tramway from about 1924.

[84] In 1906 the village had a Midland Railway (burnt down 1926)[109] and a Totara Flat, hotel,[110] butter factory, school, Roman Catholic and Presbyterian churches, small public hall, 2 stores, butchery and bakery.

[143][144] The original Reefton station opened on the south bank of the river on 29 February 1892,[147] when the line was extended from Tawhai.

It had a booking-office, luggage-room, public lobby, ladies' waiting-room, telephone, coal-store, guards' and lamp rooms and was made in sections to allow for removal.

Both required expensive cuttings, bridges and tunnels to get through the deep and narrow Upper and Lower Buller Gorges.

The Lower Gorge was the most difficult section of the railway, with 12 bridges, totalling 3,603 ft (1,098 m), and 5 short tunnels in its 18.5 mi (29.8 km).

[219] Work on the Westport – Inangahua railway stopped again on 21 October 1931[220] and restarted on 30 July 1936,[54] after election of a Labour Government.

PWD started running goods trains beyond Inangahua from 24 April 1942 and passengers from Monday, 7 September 1942 using the new railcars.

Prior to that Inangahua's Class F shunter was sent to Westport in exchange for a diesel tractor from Mackley ballast pit.

[233] In 1950 Te Kuha goods shed was moved to Elmer Lane maintenance depot, Greymouth, and the siding was lifted.

[298] In March 2022 Toki bridge was opened in place of the old footbridge to the goods shed,[299] where the Westport Railway Preservation Society, formed in March 1993, had one of the line's original engines, a NZR C class (1873), rescued from a dump in Buller Gorge,[300] a Milburn Cement shunter, a guard’s van and various wagons.

[301] The area was damaged by flooding in 2022 and the shed was demolished in 2023, after rehousing the preserved stock,[302] some at the National Railway Museum of New Zealand.

) These graphs show the variation over time in passenger numbers at Westport, Inangahua, Reefton and Ngahere (detail shown in table below).

[304] Access from the main road and camps was by a cableway for materials, 3 ferries on cables for workmen and a suspension bridge.

[309] The camp, beside the main road at Ohika, had 5 married men's cottages, 47 single huts, a cookhouse and a bathhouse.

It had a YMCA recreation hall (opened about 1928), bath houses, a tennis court,[311][312][313][314] 9 married men's cottages, 63 single huts, a school for 30 children and an office.

[325] Highway Camp, also known as Petticoat Lane, south of Hawks Crag, had 3 houses and 10 huts for road construction workers.

[310] Blackwater Camp had an overseer’s house and 12 huts on the Newmans stables site,[310] east of Hawk's Crag.