Tadami Line

The line grew from two separate roots that were not joined for more than four decades. Its eastern end began as the Aizu Line (会津線), planned under the Light Railway Act: on 15 October 1926 the Aizu-Wakamatsu–Aizu-Bange section (21.6 km) opened, followed by an extension to Aizu-Yanaizu (11.7 km) on 20 November 1928. The Aizu-Yanaizu–Koide corridor was designated a planned line under the amended Railway Construction Act as the railway 'from Yanaizu in Fukushima via Tadami to Koide in Niigata.' The eastern section was pushed on to Aizu-Miyashita (12.1 km) on 28 October 1941.

Meanwhile the western end opened independently as the Tadami Line: on 1 November 1942 the Koide–Ōshirakawa section (26.0 km) entered service. After the Second World War the eastern section was extended again to Aizu-Kawaguchi (15.4 km) on 20 September 1956, partly to serve the construction of the Tagokura and Taki dams. From the Aizu-Kawaguchi railhead a dedicated railway built by the Electric Power Development Company carried dam-construction freight to the Tagokura site between 1957 and 1961; once Tagokura Dam was complete this alignment was upgraded and opened as a national railway line to Tadami (27.6 km) on 20 August 1963.

The final link came on 29 August 1971, when the Tadami–Ōshirakawa section (20.8 km) — built by the Japan Railway Construction Public Corporation as the 'Tadami Central Line' and operated for passengers only — opened to traffic. On the same day the western Koide–Ōshirakawa stretch was absorbed into the eastern route, the Nishi-Wakamatsu–Aizu-Takinohara branch was separated off to form a new Aizu Line, and the through Aizu-Wakamatsu–Koide route of 135.2 km became the Tadami Line as it is known today. Steam locomotives made their last regular run on 31 October 1974, and freight services were withdrawn between 1980 and 1982.

Upon the privatisation of Japanese National Railways on 1 April 1987 the line passed to JR East as a Class 1 railway operator, while JR Freight took on Class 2 freight rights over the short Nishi-Wakamatsu–Aizu-Wakamatsu section. As a heavy-snow, lightly used rural line the Tadami Line was repeatedly interrupted by natural disasters: the 2004 Chūetsu earthquake closed the Tadami–Koide section that October until 20 November, and landslides and storms cut the line in 2005 and again in 2015.

The defining event came on 30 July 2011, when torrential rain in the Niigata–Fukushima downpour washed away the fifth, sixth and seventh Tadami River bridges between Aizu-Kawaguchi and Aizu-Ōshio and destroyed track formation near Aizu-Yanaizu, severing the line over the 113.6 km between Aizu-Bange and Koide. Most sections were repaired within weeks or months, and the Tadami–Ōshirakawa portion reopened on 1 October 2012, but the 27.6 km between Aizu-Kawaguchi and Tadami — including the costly bridge reconstructions — was left out of service, replaced by a substitute bus while its future was debated. Tagokura Station was abolished in 2013 and Kakinoki Station in 2015, both for very low use.

Restoration of the severed section proved drawn-out and contentious, since as a profitable company JR East did not qualify for the disaster-aid then available to loss-making railways, and the repair bill rose toward roughly ¥8.1 billion. In June 2017 JR East and Fukushima Prefecture agreed to rebuild the line under a vertical-separation arrangement, with the prefecture bearing two-thirds of the reconstruction cost and JR East one-third; work began in June 2018. The transport ministry licensed Fukushima as the Class 3 (infrastructure-holding) operator and JR East as the Class 2 (train-operating) operator in November 2021, and on 1 October 2022 the Aizu-Kawaguchi–Tadami section reopened, restoring through running over the whole line for the first time in eleven years. From that day the reopened section runs under the vertical-separation model — Fukushima Prefecture owning the infrastructure and JR East operating the trains — and one-man operation began between Aizu-Wakamatsu and Tadami.

• 192615 October: the Aizu Line (Aizu-Wakamatsu–Aizu-Bange, 21.6 km), the line's eastern origin, opens under the Light Railway Act.
• 192820 November: the Aizu Line is extended from Aizu-Bange to Aizu-Yanaizu (11.7 km).
• 194128 October: the eastern section is extended from Aizu-Yanaizu to Aizu-Miyashita (12.1 km).
• 19421 November: the western section opens as the Tadami Line, Koide to Ōshirakawa (26.0 km).
• 195620 September: the eastern section is extended from Aizu-Miyashita to Aizu-Kawaguchi (15.4 km), partly to serve construction of the Tagokura and Taki dams.
• 196320 August: after the Tagokura Dam is completed, the upgraded dam-construction alignment opens as a national railway from Aizu-Kawaguchi to Tadami (27.6 km).
• 197129 August: the passenger-only Tadami–Ōshirakawa section (20.8 km) opens, joining the two ends; the through Aizu-Wakamatsu–Koide route (135.2 km) becomes the Tadami Line and the Nishi-Wakamatsu–Aizu-Takinohara branch is split off as a new Aizu Line.
• 197431 October: steam locomotives make their last regular run on the line.
• 19821 August: freight services are abolished on the Nishi-Wakamatsu–Tadami section (having ended on Ōshirakawa–Koide in 1980).
• 19871 April: on the privatisation of Japanese National Railways, the line passes to JR East as a Class 1 operator; JR Freight takes Class 2 rights over Nishi-Wakamatsu–Aizu-Wakamatsu.
• 200423 October: the Chūetsu earthquake severs the Tadami–Koide section; service is restored on 20 November.
• 201130 July: the Niigata–Fukushima heavy rain washes away Tadami River bridges Nos. 5–7 between Aizu-Kawaguchi and Aizu-Ōshio and destroys track near Aizu-Yanaizu, severing the line over 113.6 km between Aizu-Bange and Koide.
• 20121 October: the Tadami–Ōshirakawa section is restored, leaving only Aizu-Kawaguchi–Tadami (27.6 km) out of service, served by a replacement bus.
• 20221 October: the Aizu-Kawaguchi–Tadami section reopens after 11 years, restoring through service over the whole line; the reopened section adopts vertical separation (Fukushima Prefecture as Class 3 infrastructure holder, JR East as Class 2 operator) and one-man operation begins between Aizu-Wakamatsu and Tadami.