Ban'etsu West Line

From Kōriyama the line climbs west into the Aizu basin, passing Bandai-Atami and skirting the northern shore of Lake Inawashiro beneath Mount Bandai before reaching Aizu-Wakamatsu, the historic castle town that is the line's principal intermediate hub. North of Aizu-Wakamatsu the route continues through Kitakata, while the longer western half runs down the valley of the Agano River (the Aganogawa) through Nozawa and Tsugawa toward Gosen and Niitsu. The valley scenery of the Agano, together with Lake Inawashiro and the volcanic cone of Mount Bandai, gives the line much of its tourist appeal; the Aizu-Wakamatsu–Niitsu section carries the nickname "the railway of forests, water and romance" (森と水とロマンの鉄道).

The line is partly electrified and partly diesel-operated. The eastern section from Kōriyama to Aizu-Wakamatsu, a distance of 64.6 km, is electrified at 20 kV AC, 50 Hz using overhead catenary, while the western section from Aizu-Wakamatsu to Niitsu, 111.0 km, is non-electrified and worked by diesel railcars. The Japanese-language infobox gives the maximum speed as 95 km/h. Local trains form the backbone of service, with rapid trains additionally running on the electrified Kōriyama–Aizu-Wakamatsu portion, alongside seasonal sightseeing trains.

The railway opened in stages from the turn of the twentieth century, and its two ends were originally built by different undertakings. The Kōriyama end was opened by the private Iwaetsu Railway, which began operating from Kōriyama to Nakayamajuku (21.5 km) on 26 July 1898 and reached Wakamatsu (later Aizu-Wakamatsu) the following year; the company was nationalised on 1 November 1906. The Niitsu end was built from the Shin'etsu Line side, the Niitsu–Magoshita section opening on 25 October 1910 and the Magoshita–Tsugawa extension on 1 June 1913. The two halves were joined when the Nozawa–Tsugawa section opened on 1 November 1914, completing a through route across the mountains.

For a brief period after through-running began the western portion was treated as part of the Shin'etsu Main Line, but on 10 October 1917 the whole Kōriyama–Niitsu route was reorganised and given the name Ban'etsu West Line, distinguishing it from the Ban'etsu East Line east of Kōriyama. Under Japanese National Railways the Kōriyama–Kitakata section was electrified at 20 kV AC on 15 June 1967, and limited express services such as the Aizu (later branded Aizu Yamabata and Viva Aizu) ran over the line in the later twentieth century. On 1 April 1987, with the privatisation of Japanese National Railways, the line passed to JR East, with freight operations taken over by JR Freight.

Since 1987 the line has become known for its tourist trains. On 29 April 1999 the steam-hauled rapid "SL Banetsu Monogatari" began operating between Aizu-Wakamatsu and Niitsu, drawn by the preserved Class C57 locomotive C57 180; it runs semi-regularly, chiefly on Saturdays, Sundays and holidays from April to November, and is associated with the crossing of the Ichinotogawa River bridge. A new station, Kōriyamatomita, opened on 1 April 2017. In the twenty-first century parts of the line have also been affected by natural disasters and by changes to its electrified network.

On 4 August 2022 heavy rain caused a support pier of a railway bridge between Kitakata and Yamato (over the Nigorigawa) to collapse, suspending service over the western part of the line; full service was restored on 1 April 2023 once the bridge had been rebuilt. Electric operation on the Aizu-Wakamatsu–Kitakata portion ceased in March 2022, and the electrification of the Aizu-Wakamatsu–Kitakata section was formally abolished on 17 May 2024, so that the present continuously electrified section runs only as far west as Aizu-Wakamatsu.

• 189826 July: the private Iwaetsu Railway opens its first section, Kōriyama to Nakayamajuku (21.5 km).
• 1899The Iwaetsu Railway extends west, reaching Wakamatsu (later Aizu-Wakamatsu) (Yamagata–Wakamatsu section opened 15 July).
• 190420 January: the Wakamatsu–Kitakata section is opened.
• 19061 November: the Iwaetsu Railway (Kōriyama–Kitakata) is nationalised.
• 191025 October: from the Niitsu end, the Shin'etsu Line branch Niitsu–Magoshita section (17.2 km) opens.
• 19131 June: the Magoshita–Tsugawa section (21.4 km) opens, extending the line from the Niitsu side.
• 19141 November: the Nozawa–Tsugawa section opens, joining the two ends into a through route across the mountains.
• 191710 October: the Kōriyama–Niitsu route is reorganised and renamed the Ban'etsu West Line (distinguishing it from the Ban'etsu East Line).
• 1965Japanese National Railways introduces limited express service over the line, as part of the Yamabata service between Ueno and Aizu-Wakamatsu (later renamed Aizu Yamabata in 1968 and Viva Aizu from 1993).
• 196715 June: the Kōriyama–Kitakata section is electrified at 20 kV AC.
• 19871 April: with the privatisation of Japanese National Railways, the line is succeeded by JR East, with freight operated by JR Freight.
• 199929 April: the steam-hauled rapid "SL Banetsu Monogatari", drawn by the preserved Class C57 locomotive C57 180, begins operating between Aizu-Wakamatsu and Niitsu.
• 20021 December: the limited express "Viva Aizu" is renamed "Aizu".
• 20171 April: a new station, Kōriyamatomita, opens between Kōriyama and Kikuta.
• 20224 August: heavy rain causes a pier of a railway bridge (the Nigorigawa bridge) between Kitakata and Yamato to collapse, suspending service on the western part of the line. Electric services on the Aizu-Wakamatsu–Kitakata portion had ceased earlier, in March.
• 20231 April: reconstruction of the Nigorigawa bridge between Kitakata and Yamato is completed and full service is restored.
• 202417 May: the electrification of the Aizu-Wakamatsu–Kitakata section is formally abolished, leaving the continuously electrified section running only as far west as Aizu-Wakamatsu.