Sekihoku Main Line

The line as it exists today was not built as a single project but stitched together from three earlier routes aimed at reaching Kitami and Abashiri: the Yūbetsu Line route running from Nayoro via Okoppe and Engaru to Kitami, the Abashiri Main Line route from Ikeda in the Tokachi region through Kitami to Abashiri, and the Sekihoku Line itself — a shortcut from Asahikawa over the Kitami Pass to Engaru. The earliest piece opened on the Abashiri side: the Abashiri Line reached Notsukeushi (later renamed Kitami) on 25 September 1911, and on 5 October 1912 it was extended to the first Abashiri Station, completing a through route from Ikeda; the Ikeda–Abashiri route was renamed the Abashiri Main Line on 18 November 1912.

The central, mountain-crossing section was the last and hardest to build. On 18 November 1912 the Yūbetsu Light Railway opened between Notsukeushi and Rubeshibe; it was extended east toward Engaru in stages from 1914 as a narrow 762 mm gauge line, regauged to 1,067 mm between Rubeshibe and Engaru in 1916, and renamed the Yūbetsu Line in 1922. Meanwhile a state-built line approached from the Asahikawa side: the Sekihoku Line opened from Shin-Asahikawa to Aibetsu on 4 November 1922 and reached Kamikawa in 1923. In 1927 the Asahikawa-side line was renamed the Sekihoku West Line and a Sekihoku East Line was begun from Engaru, the two halves then driving toward each other across the Kitami Pass.

The through connection was completed on 1 October 1932, when the Sekihoku East Line's Nakakoshi–Shirataki segment opened — carrying the line over the difficult Kitami Pass through the new Sekihoku Tunnel and finally giving Asahikawa its shortest rail route to the Kitami and Abashiri districts. On the same day the Yūbetsu Line's Engaru–Notsukeushi section was absorbed and the combined Shin-Asahikawa–Notsukeushi route was renamed the Sekihoku Line. Construction of the pass section is also remembered for its harshness: the nearby Jōmon Tunnel, dug during the earlier Yūbetsu-line works, became notorious for the deaths of forced labourers, and human remains were later recovered from within it.

Notsukeushi was renamed Kitami on 1 October 1942, and on 1 June 1949 the line passed to the newly created Japanese National Railways (JNR) along with the rest of the national network. The line took on its present name and shape on 1 April 1961, when a route reorganisation merged the Sekihoku Line with the Kitami–Abashiri portion of the Abashiri Main Line, and the whole 234.0-kilometre Shin-Asahikawa–Abashiri route was renamed the Sekihoku Main Line. The switchback layout that survives at Engaru Station — where trains reverse direction — is a lasting reminder of how the line was assembled from separate routes.

Under JNR the route became the spine of limited-express travel to the Okhotsk coast. A semi-express named Okhotsk began running between Asahikawa and Abashiri in 1959, a limited express Ōtori was introduced between Hakodate and Abashiri in 1964, and from 1972 the limited express Okhotsk linked Sapporo with Abashiri. The line also has a place in steam history: on 24 December 1971 the Taisetsu No. 6, the last steam-locomotive-hauled express train anywhere in Japan, was switched to diesel haulage. In 1977 the Kitami Tunnel opened, taking the line underground through Kitami in what is described as Japan's first continuous grade-separation project carried out by undergrounding.

The Sekihoku Main Line passed to JR Hokkaido on 1 April 1987 with the privatisation of JNR, JR Hokkaido becoming the first-type operator of the whole line and the new JR Freight the second-type operator over the Shin-Asahikawa–Kitami section. One-man operation of local trains began across the line on 14 March 1992. In the decades since, thinning rural ridership has steadily pared the line back: many minor halts have closed or been downgraded to signal points, including Kami-Shirataki and Kyū-Shirataki in 2016, four more stations in 2021, and Aizan in 2024. In August 2016 typhoons severely damaged the mountain section, suspending services and forcing freight to be moved by road for a time.

Today the line still carries the limited express Okhotsk twice daily between Sapporo and Abashiri, supplemented by the Taisetsu and the rapid Kitami running between Asahikawa and Abashiri, alongside sparse local services divided roughly into Asahikawa-area, mountain, and Kitami–Abashiri segments. Each autumn-to-spring season a seasonal freight working known as the "onion train" carries the region's harvested onions and other produce from Kitami to Shin-Asahikawa, hauled in push-pull formation to cope with the Kitami and Jōmon passes. The line's future, however, is uncertain: on 18 November 2016 JR Hokkaido named it among routes it cannot sustain on its own, and its long-term survival is now the subject of discussion with local governments and JR Freight.

• 191125 September: the Abashiri Line reaches Notsukeushi (later Kitami) from Rikubetsu, establishing Notsukeushi Station.
• 19125 October: the Abashiri Line is extended Notsukeushi–Abashiri (first station), completing the Ikeda–Abashiri route; renamed the Abashiri Main Line on 18 November. Same day (18 Nov) the Yūbetsu Light Railway opens Notsukeushi–Rubeshibe.
• 19145 October: the Yūbetsu Light Railway (762 mm gauge) opens east of Rubeshibe toward Ikutahara.
• 19167 November: the Rubeshibe–Engaru section is regauged from 762 mm to 1,067 mm.
• 19224 November: the state-built Sekihoku Line opens Shin-Asahikawa–Aibetsu. (The Yūbetsu route had been renamed the Yūbetsu Line on 2 September.)
• 192315 November: the Sekihoku Line is extended Aibetsu–Kamikawa.
• 192710 October: Shin-Asahikawa–Kamikawa is renamed the Sekihoku West Line; the Sekihoku East Line opens Engaru–Maruseppu.
• 192912 August: the Sekihoku East Line is extended Maruseppu–Shirataki; on 20 November the West Line reaches Nakakoshi (Kamikawa–Nakakoshi).
• 19321 October: the Nakakoshi–Shirataki segment opens through the new Sekihoku Tunnel over the Kitami Pass, completing the through route; the Yūbetsu Line's Engaru–Notsukeushi section is absorbed and Shin-Asahikawa–Notsukeushi is renamed the Sekihoku Line.
• 19421 October: Notsukeushi Station is renamed Kitami Station.
• 19491 June: the line is transferred to the newly formed Japanese National Railways (JNR).
• 19611 April: a route reorganisation merges the Sekihoku Line with the Kitami–Abashiri portion of the Abashiri Main Line; the whole Shin-Asahikawa–Abashiri route (234.0 km) is renamed the Sekihoku Main Line.
• 197124 December: the Taisetsu No. 6, the last steam-locomotive-hauled express train in all of Japan, is switched to diesel haulage.
• 197718 September: the Kitami Tunnel takes the line underground through Kitami, described as Japan's first continuous grade-separation by undergrounding.
• 19871 April: with the privatisation of JNR, JR Hokkaido becomes first-type operator of the whole line and JR Freight the second-type operator over Shin-Asahikawa–Kitami.
• 199214 March: one-man operation of local trains begins across the line.
• 201626 March: Kami-Shirataki and Kyū-Shirataki stations close, with Shimo-Shirataki and Kanehana downgraded to signal points. In August, typhoons damage the mountain section, suspending services and forcing freight onto road substitution; on 18 November JR Hokkaido lists the line among those it cannot maintain alone.
• 202415 March: Aizan Station closes, continuing the steady reduction of minor stations on the line (four more had closed on 13 March 2021).