Akita Nairiku Line

The line as it exists today was stitched together from two former Japanese National Railways (JNR) branch lines that for decades approached each other from opposite ends without meeting. The northern half began as the Aniai Line (阿仁合線), whose first segment, from Takanosu (then written Takanosu, 鷹ノ巣) to Yonaizawa, opened on 10 December 1934 over a length of 15.1 kilometres. The line was pushed south in stages: it reached Ani-Maeda on 15 November 1935 and Aniai on 25 September 1936, and after a long pause was finally extended to Hitachinai on 15 October 1963.

The southern half began much later as the Kakunodate Line (角館線), which opened from Kakunodate to Matsuba on 1 November 1970. A connecting link through the mountains between Hitachinai and Matsuba was planned, which would have joined the two lines into a single interior trunk route, but construction of that link was suspended in the 1980s amid JNR's deepening financial crisis, leaving a gap of roughly 30 kilometres in the centre.

Both lines were caught up in the rationalisation of JNR's loss-making rural network. The Kakunodate Line was approved for abolition as a first-batch "specified local line" on 18 September 1981, and the Aniai Line was approved as a second-batch specified local line on 22 June 1984. Rather than close them outright, local interests organised a third-sector company, the Akita Nairiku Jūkan Railway, to take them over and to complete the long-deferred central link.

On 1 November 1986 JNR formally abolished both the Aniai Line and the Kakunodate Line, and on the same day the two were transferred to the new company, which operated them as the Akita Nairiku North Line and the Akita Nairiku South Line. The station at the northern terminus was renamed from Takanosu (鷹ノ巣) to Takanosu (鷹巣) to distinguish it in writing from the adjacent JNR station of the same reading.

The through route was completed on 1 April 1989, when the missing 29-kilometre section between Hitachinai and Matsuba opened. On that day the North Line absorbed the South Line and the unified railway was renamed the Akita Nairiku Line; seven new stations were opened along the new central section, among them Aniai-Matagi, named for the region's traditional Matagi hunters, and the express "Moriyoshi" began running two round trips a day.

In its third-sector decades the line has leaned increasingly on tourism and branding. It was given the nickname "Akita Bijin Line" ("Akita beauty line") in 2012, then renamed "Smile Rail Akita Nairiku Line" on 1 November 2017, and several stations were renamed to advertise local attractions — Oga became Jōmon-Oga in 2020 and Ani-Maeda became Ani-Maeda-Onsen in 2021. Like many lines threading steep, snowbound mountain valleys, it has also suffered repeated weather damage: heavy rain in 2022 and again in the summer of 2024 severed sections for months at a time before full operation was restored, underscoring both the line's vulnerability and the local commitment to keeping it open.

• 193410 December: JNR opens the Aniai Line's first segment, Takanosu–Yonaizawa, over 15.1 km.
• 193515 November: the Aniai Line is extended from Yonaizawa to Ani-Maeda.
• 193625 September: the Aniai Line is extended from Ani-Maeda to Aniai.
• 196315 October: the Aniai Line is extended from Aniai to Hitachinai.
• 19701 November: JNR opens the Kakunodate Line from Kakunodate to Matsuba.
• 198118 September: the Kakunodate Line is approved for abolition as a first-batch 'specified local line'.
• 198422 June: the Aniai Line is approved for abolition as a second-batch 'specified local line'.
• 19861 November: JNR abolishes both the Aniai Line and the Kakunodate Line; the same day they transfer to the new third-sector Akita Nairiku Jūkan Railway, becoming the Akita Nairiku North Line and South Line. Takanosu Station's writing changes from 鷹ノ巣 to 鷹巣.
• 19891 April: the missing Hitachinai–Matsuba link (~29 km) opens; the North Line absorbs the South Line and the route is renamed the Akita Nairiku Line. Seven new stations open (including Aniai-Matagi) and the express 'Moriyoshi' begins running twice daily each way.
• 20011 December: one of the two daily round trips of the 'Moriyoshi' express is discontinued.
• 201227 January: the line is given the nickname 'Akita Bijin Line' (Akita beauty line).
• 20171 November: the line's nickname is changed to 'Smile Rail Akita Nairiku Line'.
• 202014 March: Oga Station is renamed Jōmon-Oga.
• 202113 March: Ani-Maeda Station is renamed Ani-Maeda-Onsen.
• 2022August–December: heavy rain damages the line between Yonaizawa and Maeda-Minami, suspending Takanosu–Aniai; full operation resumes on 12 December.
• 2024July–August: record heavy rain damages multiple locations; service is restored in stages, with full operation resuming on 10 August.