Chikuhō Main Line

The railway was a private coal venture from the start. It was built by the Chikuhō Kōgyō Railway (筑豊興業鉄道), which opened its first section, from Wakamatsu to Nōgata, on 30 August 1891, establishing stations at Wakamatsu, Orio, Nakama and Nōgata. Coal traffic drove a rapid southward push up the valley of the Onga River: the line reached Kotake in 1892 and Iizuka in 1893. In 1894 the company renamed itself the Chikuhō Railway (筑豊鉄道), and in 1895 it extended service onward from Iizuka toward Usui, opening up the Kamiyamada district.

From the outset the line was duplicated section by section to separate slow coal trains from passenger trains. The Wakamatsu–Nōgata corridor was double-tracked between 1893 and 1896, the last stretch being Wakamatsu–Orio in 1896. Further doubling followed under state ownership, with the Nōgata–Kotake section completed by 1906 and the Kotake–Iizuka section finally double-tracked during the Second World War, between 1942 and 1944. This repeated track-laying reflected the line's role as the central artery of coal transport in the Chikuhō region.

The Chikuhō Railway was absorbed by the larger Kyushu Railway (九州鉄道) on 1 October 1897, and that company in turn was nationalised on 1 July 1907 under the Railway Nationalization Act, bringing the line into the government railways. On 12 October 1909 the national line-naming order formally created the name "Chikuhō Main Line" for the Wakamatsu–Kamiyamada route together with several coal branches, while the separate Iizuka–Nagao and Nagao–Mameda lines were designated the Nagao Line.

The through route to Haruda was completed in stages over the following two decades. The Nagao Line was extended from Nagao to Chikuzen Uchino on 15 July 1928, and on 7 December 1929 the final segment from Chikuzen Uchino to Haruda opened, establishing Chikuzen Yamae Station. With that opening the Wakamatsu–Iizuka trunk, the Nagao Line and the new track were combined into a single Chikuhō Main Line running Wakamatsu–Haruda, and the Iizuka–Kamiyamada portion was split off as the separate Kamiyamada Line. In 1940 Nagao Station, near the line's southern junction, was renamed Keisen.

Through the mid-twentieth century the Chikuhō Main Line remained one of Japan's busiest coal railways, worked by Pacific-type and freight steam locomotives until 1975, and from 1950 to 1985 it also carried a succession of express and sleeper services routed between Honshū and Kyushu via Orio and Haruda. But the Chikuhō coalfield was exhausted: its collieries closed completely by 1976, the web of coal branch lines that fed the main line was abandoned, and after the 1987 break-up of Japanese National Railways the parallel Kamiyamada Line was itself discontinued in 1988. The last through limited express, the sleeper "Akatsuki," stopped using the line in 1985.

With Japanese National Railways privatised on 1 April 1987, the Chikuhō Main Line passed to JR Kyushu, which took over the whole line, while Japan Freight Railway (JR Freight) held second-class operating rights over the Orio–Nōgata section. As the population of the Fukuoka metropolitan area grew, the line was reinvented as a commuter route. On 6 October 2001 the Orio–Keisen section was electrified at 20 kV 60 Hz, and at the same time JR Kyushu introduced the service names still in use today: "Fukuhoku Yutaka Line" for the electrified Orio–Keisen section (combined with the Sasaguri Line toward Hakata), "Wakamatsu Line" for the non-electrified Wakamatsu–Orio section, and "Haruda Line" for the non-electrified Keisen–Haruda section.

The line's three sections have since developed very different characters. The Wakamatsu Line, double-tracked but left unelectrified, was chosen as a testbed for battery-electric trains and is now worked by BEC819 series "DENCHA" units. The electrified Fukuhoku Yutaka Line carries dense electric-multiple-unit commuter service between Kitakyushu, Nōgata and Hakata. The lightly used Haruda Line, which crosses the Mizukoshi Pass, runs only a handful of diesel trains a day; the July 2018 heavy rains damaged its track and suspended the Keisen–Haruda section, which reopened on 9 March 2019 after about eight months out of service.

• 189130 August: the Chikuhō Kōgyō Railway opens its first section, Wakamatsu–Nōgata, establishing Wakamatsu, Orio, Nakama and Nōgata stations.
• 189228 October: the line is extended from Nōgata to Kotake, opening Kotake Station.
• 18933 July: the line is extended from Kotake to Iizuka, opening Namazuta and Iizuka stations.
• 189415 August: the Chikuhō Kōgyō Railway renames itself the Chikuhō Railway.
• 18955 April: service is extended from Iizuka toward Usui, opening the line toward the Kamiyamada district.
• 189629 April: the Wakamatsu–Orio section is double-tracked, completing duplication of the Wakamatsu–Nōgata corridor.
• 18971 October: the Chikuhō Railway is merged into the larger Kyushu Railway.
• 19071 July: the Kyushu Railway is nationalised under the Railway Nationalization Act; the line becomes part of the government railways.
• 190912 October: the national line-naming order formally creates the name 'Chikuhō Main Line' for the Wakamatsu–Kamiyamada route and several coal branches; the Iizuka–Nagao and Nagao–Mameda lines become the Nagao Line.
• 192815 July: the Nagao Line is extended from Nagao to Chikuzen Uchino, opening Kami-Honami and Chikuzen Uchino stations.
• 19297 December: the Chikuzen Uchino–Haruda section opens (establishing Chikuzen Yamae Station); the Wakamatsu–Iizuka trunk, the Nagao Line and the new track are combined into the Wakamatsu–Haruda Chikuhō Main Line, and Iizuka–Kamiyamada is split off as the Kamiyamada Line.
• 198514 March: the sleeper limited express 'Akatsuki' ceases running via the line, ending through limited-express service over the Chikuhō Main Line.
• 19871 April: with the break-up of Japanese National Railways, JR Kyushu takes over the whole line and Japan Freight Railway (JR Freight) holds second-class operating rights over the Orio–Nōgata section.
• 20016 October: the Orio–Keisen section is electrified at 20 kV 60 Hz AC, and the service names 'Fukuhoku Yutaka Line' (Orio–Keisen), 'Wakamatsu Line' (Wakamatsu–Orio) and 'Haruda Line' (Keisen–Haruda) are introduced.
• 20186 July: the Keisen–Haruda (Haruda Line) section is damaged in the July 2018 heavy rains and suspended.
• 20199 March: the Keisen–Haruda section reopens after about eight months out of service.