Ikawa Line

The line was not built as a public railway at all but as an industrial line for hydroelectric construction. It opened on 20 March 1935 as the Ōigawa Electric Company's private 'Ōigawa Dedicated Tramway' between Senzu and the Ōigawa Power Station (now closed), carrying workers and materials up the valley to build dams. It was laid at first to the light 762 mm gauge and worked by internal-combustion power. The following year, on 19 November 1936, it was regauged to 1,067 mm so that freight wagons could run through; because the Sumatagawa dedicated tramway (the later Senzu Forest Railway) still used 762 mm, the Senzu–Sawama stretch was given a three-rail dual-gauge track. The cramped origins left a permanent mark — the tunnels and rolling stock remain unusually small, smaller even than typical light-railway equipment.

The railway then passed through the hands of the region's electric utilities. In 1954 it was extended as a private line of the Chubu Electric Power Company, reaching beyond the present Ikawa terminus to Dōdaira to serve construction of the Ōigawa Dam, and was renamed the Chubu Electric Dedicated Railway. In 1959 the railway operation was spun out of the utility: on 1 August 1959 the Ōigawa Railway took it over as the Ōigawa Railway Ikawa Line and began carrying fare-paying passengers, the line's first public operation under the Local Railway Act. The asset ownership and the covering of operating losses remained with Chubu Electric, an arrangement that persists to this day.

The early decades brought contraction at both ends. When the Senzu Forest Railway was abolished in 1969, the 762 mm rail of the Senzu–Sawama dual-gauge section was removed afterward. On 1 April 1971 the line was trimmed at its far end, with the Ikawa–Dōdaira section closed and the Kamekubo signal station abolished, leaving Ikawa as the terminus it remains today. From 1970 the company also ran a small sightseeing 'mini-SL' steam train on a siding beside the Senzu–Kawane-Ryōgoku section, an early sign of the tourist orientation that would later define the line; that mini-SL operation ran until late 1989.

The line's defining transformation came with the Nagashima Dam. The dam, begun in 1972 and completed in 2002, raised a reservoir that would have flooded part of the route; rather than accept compensation and close, the railway built a new alignment along the new lakeshore. Because the new line included a steep 90-per-mille (9%) grade, the company adopted the Abt rack system — a technology that had vanished from Japan in 1963 when the rack section over the Usui Pass on the Japanese National Railways' Shin'etsu Main Line was abolished. The rebuilt section opened on 2 October 1990: the old Kawane-Ichishiro station was relocated and renamed Abt Ichishiro, Kawane-Nagashima became Sessokyō Onsen, and the Abt Ichishiro–Nagashima Dam segment was electrified at 1,500 V DC as the rack section, while the new stations of Nagashima Dam, Hiranda and Okuōikojō opened on the relocated route. To this day trains are hauled and pushed by DD20 diesel locomotives, with an ED90 electric rack locomotive coupled on for the rack climb.

Since then the Ikawa Line has leaned ever further into tourism while contending with the fragility of its mountain setting. In 1999 the line was given its 'South Alps Abt Line' nickname, and a line-wide automatic train stop system entered service in 2009. Landslides and typhoons have repeatedly severed the upper section for months at a time over the 2000s, 2010s and 2020s. In 2022 a 'Thomas the Tank Engine' character train, 'Toby', began running on the Senzu–Okuizumi section. In 2026 the operator moved to recast the line explicitly as a tourist railway: after announcing in April a flat fare of 3,500 yen per ride and a reservation-based sightseeing model — a plan that drew objections from residents and was briefly postponed in May — it confirmed on 2 June that the switch to tourist-train operation would take effect from 1 July 2026.

• 193520 March: opens as the Ōigawa Electric Company's private 'Ōigawa Dedicated Tramway', Senzu–Ōigawa Power Station (now closed), at 762 mm gauge with internal-combustion power; Kawane-Ryōgoku and Sawama stations open.
• 193619 November: regauged to 1,067 mm so freight wagons can run through; the Senzu–Sawama section is laid with three-rail dual gauge for the 762 mm Sumatagawa tramway (later Senzu Forest Railway).
• 19541 April: extended as the Chubu Electric Power Company's private railway, Ōigawa Dam–Dōdaira (beyond present Ikawa), to serve construction of the Ōigawa Dam; renamed the Chubu Electric Dedicated Railway.
• 19591 August: the Ōigawa Railway takes over the Chubu Electric dedicated railway as the Ōigawa Railway Ikawa Line and begins passenger service — the line's first public operation under the Local Railway Act.
• 1969The Senzu Forest Railway is abolished; afterward the 762 mm rail of the Senzu–Sawama dual-gauge section is removed.
• 1970November: a sightseeing 'mini-SL' steam train begins running on a siding paralleling the Senzu–Kawane-Ryōgoku section.
• 19711 April: the Ikawa–Dōdaira section is abolished and the Kamekubo signal station is closed, leaving Ikawa as the terminus.
• 198926 November: the mini-SL sightseeing train ends operation.
• 19902 October: with the Nagashima Dam reservoir flooding part of the route, a new lakeshore alignment opens; old Kawane-Ichishiro is relocated and renamed Abt Ichishiro and Kawane-Nagashima becomes Sessokyō Onsen, the Abt Ichishiro–Nagashima Dam segment is electrified (1,500 V DC) as the Abt rack section, and Nagashima Dam, Hiranda and Okuōikojō stations open.
• 19991 August: the line is given the nickname 'South Alps Abt Line'.
• 200929 March: an automatic train stop (ATS) system enters service across the whole line.
• 202219 August: the 'Thomas the Tank Engine' character train 'Toby' begins running on the Senzu–Okuizumi section.
• 2026After announcing in April a flat 3,500-yen fare and a reservation-based sightseeing model — postponed in May after resident objections — the operator confirms on 2 June a switch to tourist-train operation from 1 July 2026.