Karatsu Line

The railway began as a private venture, the Karatsu Kogyo Railway, which on 1 December 1898 opened its first segment from Yamamoto through Myōken — today's Nishi-Karatsu — to a coal wharf at Ōshima, on an alignment following the west bank of the Matsuura River. The aim from the outset was to move coal from the Karatsu coalfield to the harbour. The company pressed inland the next year, opening Kyūragi to Yamamoto on 13 June 1899 and Azamihara to Kyūragi on 25 December 1899.

In April 1900 the firm renamed itself the Karatsu Railway, and on 23 February 1902 it was absorbed into the larger Kyushu Railway, one of the principal private railways of the day. The Kyushu Railway completed the line on 14 December 1903 by opening the Kubota–Azamihara section, joining the route to the national network at Kubota on what became the Nagasaki Main Line. In 1905 the original Myōken terminus was renamed Nishi-Karatsu.

Like most of Japan's major private railways, the Kyushu Railway was nationalised under the Railway Nationalization Act: it was bought out and brought into state hands on 1 July 1907, and the Karatsu Line became part of the government railways. Coal traffic remained the line's reason for being for decades, and between roughly 1898 and 1912 a number of freight-only branch lines were thrown out to individual mines, paralleling the growth of the Karatsu coalfield.

The line's relationship with the neighbouring Chikuhi Line, which it would eventually share through services with, began to take shape in 1929, when the Chikuhi Line was extended from Higashi-Karatsu to Yamamoto along the east bank of the Matsuura River, meeting the Karatsu Line there. In the post-war years the line was modernised: steam was eliminated on 15 May 1956, when trains were replaced by diesel railcars.

As coal mining around Karatsu declined, the freight network was dismantled. The Yamamoto–Kishitake branch closed on 20 August 1971, and the Nishi-Karatsu–Ōshima freight branch — the last of the coal branches — closed on 15 November 1982. The biggest single change came on 22 March 1983, when the Chikuhi Line was rebuilt to branch at Karatsu and the Karatsu–Nishi-Karatsu section was electrified at 1,500 V DC in step with the electrification of the Chikuhi Line, with centralised traffic control (CTC) installed over the whole Kubota–Nishi-Karatsu route. Freight operations over the line ceased entirely on 1 November 1986.

With the break-up and privatisation of Japanese National Railways, the Karatsu Line passed to the newly formed Kyushu Railway Company (JR Kyushu) on 1 April 1987, which has operated it since. Today every train on the line stops at all stations, and services are closely interwoven with the Chikuhi Line: through trains run from both the western (Imari) and eastern sections of the Chikuhi Line, and over the electrified Karatsu–Nishi-Karatsu stretch the line also hosts Chikuhi Line trains running through to the Meinohama direction and onto the Fukuoka City Subway Airport Line. Trains from Kubota continue over the Nagasaki Main Line to terminate at Saga.

• 18981 December: the private Karatsu Kogyo Railway opens its first segment, Yamamoto–Myōken (today Nishi-Karatsu)–Ōshima, along the west bank of the Matsuura River to carry coal to the Port of Karatsu.
• 189913 June: the line is extended inland from Yamamoto to Kyūragi.
• 189925 December: the line is extended from Kyūragi to Azamihara.
• 190018 April: the Karatsu Kogyo Railway renames itself the Karatsu Railway.
• 190223 February: the Karatsu Railway is merged into the larger Kyushu Railway.
• 190314 December: the Kubota–Azamihara section opens, completing the through line and joining it to the national network at Kubota.
• 190511 October: Myōken Station is renamed Nishi-Karatsu.
• 19071 July: the Kyushu Railway is bought out and nationalised under the Railway Nationalization Act; the Karatsu Line becomes part of the government railways.
• 1929The Chikuhi Line is extended from Higashi-Karatsu to Yamamoto along the east bank of the Matsuura River, meeting the Karatsu Line at Yamamoto.
• 195615 May: steam traction is eliminated as trains are replaced by diesel railcars.
• 197120 August: the Yamamoto–Kishitake branch line is closed.
• 198215 November: the Nishi-Karatsu–Ōshima freight branch — the last of the coal branch lines — is closed.
• 198322 March: the Chikuhi Line is rebuilt to branch at Karatsu; the Karatsu–Nishi-Karatsu section is electrified at 1,500 V DC in conjunction with Chikuhi Line electrification, and CTC is installed over the whole Kubota–Nishi-Karatsu route.
• 19861 November: freight operations over the line cease entirely.
• 19871 April: with the privatisation of Japanese National Railways, the Karatsu Line passes to the newly formed Kyushu Railway Company (JR Kyushu).