Kitakami Line

The line was built from both ends as two separate government light railways (kei-ben-sen). The western half came first: on 10 October 1920 the West Yokoguro Light Railway (Nishi-Yokoguro Keiben-sen) opened from Yokote to Ainono, a distance of 7.7 km. The following year, on 27 November 1921, it was extended a further 9.1 km from Ainono to Kurosawa. Meanwhile the eastern half opened on 25 March 1921 as the East Yokoguro Light Railway (Higashi-Yokoguro Keiben-sen), running 14.3 km from Kurosawajiri (today's Kitakami) to Yokokawame, and on 18 November 1921 it pushed a further 7.3 km from Yokokawame to Waga-Sennin.

In 1922 both railways were upgraded from light-railway to ordinary-line status and renamed on 2 September — the eastern half becoming the East Yokoguro Line and the western half the West Yokoguro Line. Construction continued from both directions through the mountains: the western line reached Rikuchū-Kawajiri (9.1 km from Kurosawa) on 16 December 1922, while the eastern line was extended from Waga-Sennin to Ōarusawa (3.7 km) on 25 October 1924.

The two halves were joined on 15 November 1924, when the remaining 9.1 km between Ōarusawa and Rikuchū-Kawajiri opened and the through route from Kurosawajiri to Yokote was completed. The West Yokoguro Line was absorbed into the East Yokoguro Line and the unified route was renamed the Yokoguro Line — a name compounded from the leading characters of Yokote and Kurosawajiri (now Kitakami). On 10 November 1954 the eastern terminus, Kurosawajiri Station, was itself renamed Kitakami Station, taking the name of the surrounding city. During this period the line was a steam-worked rural railway; a serious accident struck on 28 June 1961, when a bridge girder fell during construction work at the Washinosu bridge site, killing ten workers and seriously injuring two.

The building of the Yuda Dam reshaped the middle of the line. Diesel railcars began appearing on some services from March 1962, and on 1 December 1962 the section between Iwasawa and Rikuchū-Kawajiri was realigned for the dam, lengthening that stretch by 0.8 km, relocating Waga-Sennin and Rikuchū-Ōishi stations, and closing Ōarusawa Station in favour of a new signal box. Several intermediate stations were added in 1963, and on 20 October 1966 the route was given its present name, the Kitakami Line. Steam haulage ended on 19 March 1967 with a final run by a Class D60 locomotive.

With the privatisation of Japanese National Railways on 1 April 1987, the whole line passed to JR East, and its own freight operations ended on the same day. From October 1987 the Japan Freight Railway Company (JR Freight) took up second-class operating rights over the line and reintroduced a single seasonal freight working, which became year-round in 1989 and a scheduled service from 10 March 1990; new KiHa 100 series railcars arrived three days later. One-man operation began on 16 March 1991, and on 20 June that year three stations were renamed to highlight the line's scenic and hot-spring appeal — Rikuchū-Ōishi to Yudakinshūko, Rikuchū-Kawajiri to Hotto-Yuda and Iwate-Yuda to Yudakōgen. From 1 October 1994 the whole line was switched to a special automatic block system with centralised traffic control (CTC).

In the modern era the line has served both as a useful diversionary route and as a hard-pressed rural service. When the Tazawako Line was closed for regauging ahead of the Akita Shinkansen, limited expresses were diverted over the Kitakami Line as the "Akita Relay" from 30 March 1996 until March 1997. JR Freight suspended its freight trains on 14 March 2010, and from 16 March 2013 all services became one-man-operated. The two least-used stations, Hiraishi and Yamitsu, were closed on 12 March 2022. In 2023 heavy rain on 20 July triggered a slope failure near Yudakōgen that suspended the Hotto-Yuda–Yokote section until services resumed on 7 August; that November the operator and lineside municipalities, increasingly concerned about the line's future, ran a fare-free promotion to encourage ridership.

• 192010 October: the West Yokoguro Light Railway opens from Yokote to Ainono (7.7 km), the first segment of the future line.
• 192125 March: the East Yokoguro Light Railway opens from Kurosawajiri (now Kitakami) to Yokokawame (14.3 km); extended to Waga-Sennin on 18 November (+7.3 km). The western half is also extended Ainono–Kurosawa on 27 November (+9.1 km).
• 19222 September: both railways are upgraded from light-railway to ordinary-line status and renamed the East Yokoguro Line and West Yokoguro Line; the western line is extended Kurosawa–Rikuchū-Kawajiri on 16 December (+9.1 km).
• 192425 October: the eastern line is extended Waga-Sennin–Ōarusawa (+3.7 km). 15 November: the final Ōarusawa–Rikuchū-Kawajiri gap (9.1 km) opens, completing the Kurosawajiri–Yokote through route; the lines merge and are renamed the Yokoguro Line (from Yokote + Kurosawajiri).
• 195410 November: the eastern terminus Kurosawajiri Station is renamed Kitakami Station, after the surrounding city.
• 196128 June: a bridge girder collapses during construction work at the Washinosu bridge site, killing ten workers and seriously injuring two.
• 19621 December: the Iwasawa–Rikuchū-Kawajiri section is realigned for the Yuda Dam, lengthening it by 0.8 km, relocating Waga-Sennin and Rikuchū-Ōishi stations, and replacing Ōarusawa Station with a signal box. (Diesel railcars had entered some services from March.)
• 196620 October: the route is renamed the Kitakami Line, its present name.
• 196719 March: steam haulage ends with a final run by a Class D60 locomotive.
• 19871 April: with the privatisation of Japanese National Railways, the whole line passes to JR East and its own freight operations end; from October, JR Freight begins second-class operation and reintroduces a seasonal freight train.
• 199010 March: the JR Freight working becomes a scheduled service; KiHa 100 series diesel railcars are introduced on 13 March. One-man operation begins on 16 March 1991, and on 20 June 1991 Rikuchū-Ōishi, Rikuchū-Kawajiri and Iwate-Yuda are renamed Yudakinshūko, Hotto-Yuda and Yudakōgen.
• 19941 October: the whole line is converted to a special automatic block system with centralised traffic control (CTC).
• 199630 March: with the Tazawako Line closed for regauging ahead of the Akita Shinkansen, the 'Akita Relay' limited express is diverted over the Kitakami Line, running until March 1997.
• 201014 March: JR Freight suspends freight operations on the line.
• 202212 March: Hiraishi and Yamitsu, the two least-used stations, are closed.
• 202320 July: heavy rain causes a slope failure near Yudakōgen, suspending the Hotto-Yuda–Yokote section until services resume on 7 August; in November a fare-free promotion is run to encourage ridership amid concern for the line's future.