Toyama Chihō Railway Kamidaki Line

The corridor that the line now follows was first opened not by a private firm but by the prefecture itself. The project began as a private promotion: in April 1920 a licence to lay a railway between Horikawa-shin and Fujihashi was applied for under the name Oyama Railway, and the following month the promoters sought to rename the undertaking the Tateyama Electric Railway. The licence was granted in July 1920 and construction started that November. Before services began, however, the venture was taken over by the prefecture and renamed the Toyama Prefectural Railway in March 1921; at the same time the planned Horikawa-shin terminus was renamed Minami-Toyama. The Kamidaki section was opened together with what is today the Iwakuraji–Chigaki stretch of the Tateyama Line, as part of a single prefectural railway scheme.

The line opened in two stages in 1921. The first segment, from Minami-Toyama to Kamidaki, opened on 25 April 1921, and the continuation from Kamidaki to Iwakuraji followed on 20 August 1921. The route was conceived chiefly with freight in mind — it was laid out to serve the erosion-control works, hydroelectric construction and small-scale mining of the upper Jōganji River valley. Electrification came later in the decade: the equipment for electric working over the whole line was completed on 19 May 1927 and electric operation began on 10 June 1927 at 600 V DC. On 20 June 1937 the overhead voltage across the line was raised to 1,500 V DC, matching the electrification of the Tateyama Line and allowing through running.

In the wartime reorganisation of Japan's transport, the line passed into the hands of the company that still runs it. Under the Land Transport Business Coordination Act, the Toyama Chihō Railway was established on 1 January 1943 through the consolidation of the non-government railways of the Toyama area, and the former prefectural line became part of the new company's Tateyama Line. The connecting Fujikoshi Line had its own separate ancestry, having begun as the Toyama Light Railway's Toyama–Sasazu line of 1914 before its operator merged with the Toyama Electric Railway in 1941; it too was folded into the Toyama Chihō Railway in the 1943 consolidation, and the Inarimachi–Minami-Toyama section was electrified at 1,500 V DC.

For more than two decades the present route had no separate identity of its own, being operated as part of the Tateyama Line. That changed in 1969. By the 1960s road transport had drawn traffic away from rail, freight working was wound down, and the company rationalised its Tateyama-area network. On 1 April 1969 the Minami-Toyama–Iwakuraji section was split off and given the name Kamidaki Line, while the Terada–Iwakuraji portion of the former Gohyakkoku Line was absorbed into the Tateyama Line. Through trains between Dentetsu-Toyama and Tateyama, which until then had run over the present Kamidaki Line, were rerouted via Terada from that date.

Since the reorganisation the Kamidaki Line has settled into a purely local commuter role. One-man operation was introduced on 1 April 1996, jointly with the Fujikoshi Line, and Kosugi Station was added on 25 March 2003; system-wide station numbering was applied on 16 March 2019. All services are local trains calling at every station, operating between Dentetsu-Toyama and Iwakuraji via Minami-Toyama, with no trains continuing onto the Tateyama Line. The line and the Fujikoshi Line are run as a single entity under the name Fujikoshi–Kamidaki Line; a through service to the tram-style Toyama City Tram Line has long been studied by local government as a way to strengthen the route.

• 192026 April: a licence to lay a railway from Horikawa-shin to Fujihashi is applied for under the name Oyama Railway; in May the promoters apply to rename the venture the Tateyama Electric Railway. The licence is obtained on 6 July and construction begins on 4 November.
• 19219 March: the operator is renamed the Toyama Prefectural Railway; the planned Horikawa-shin terminus is renamed Minami-Toyama (20 March).
• 192125 April: the Minami-Toyama–Kamidaki section opens, the first part of the line, built by the Toyama Prefectural Railway.
• 192120 August: the Kamidaki–Iwakuraji section opens, completing the present route.
• 1927Electrification: the whole-line electric equipment is completed on 19 May and electric operation begins on 10 June at 600 V DC.
• 193720 June: the overhead voltage across the line is raised to 1,500 V DC, matching the Tateyama Line.
• 19431 January: under the Land Transport Business Coordination Act the Toyama Chihō Railway is founded by consolidating the area's non-government railways; the line becomes part of the company's Tateyama Line.
• 19691 April: the Minami-Toyama–Iwakuraji section is split off and named the Kamidaki Line; the Terada–Iwakuraji portion of the former Gohyakkoku Line is absorbed into the Tateyama Line, and Dentetsu-Toyama–Tateyama through trains are rerouted via Terada.
• 19961 April: one-man operation is introduced, jointly with the Fujikoshi Line.
• 200325 March: Kosugi Station opens.
• 201916 March: station numbering is applied across all stations on the Toyama Chihō Railway network.