Seibu Tamako Line

The line began not as a Seibu project but as a feeder for a suburban housing development. The land developer Hakone Land, controlled by the entrepreneur Yasujirō Tsutsumi, obtained a railway licence on 10 October 1925 for a line through what was then Kitatama District, and a licence to extend toward the newly completed Murayama Reservoir followed in 1927. To build and run the railway, Hakone Land set up a subsidiary, the Tamako Railway Company, which was incorporated on 15 January 1928. The Tamako Line opened its first segment, the 4.4-kilometre stretch from Kokubunji to Hagiyama, on 6 April 1928, and on 2 November 1928 the company also opened a short 1.0-kilometre branch, the Kodaira Line, from Hagiyama to Hon-Kodaira.

Over the next decade the Tamako Railway pushed north toward the reservoir and electrified its tracks. On 23 January 1930 it extended the line 3.6 kilometres from Hagiyama to a temporary Murayama-chōsuichi station, and on 7 May 1930 the whole Kokubunji–Murayama-chōsuichi route was electrified at 600 V DC. Steam haulage between Kokubunji and Hagiyama was abolished on 12 April 1934. The line reached its final length on 30 December 1936, when the last 0.9-kilometre section to Murayama-chōsuichi station opened; the earlier temporary station was renamed Musashi-Yamato and moved to its present site, completing the full Kokubunji–reservoir route.

On 12 March 1940 the Tamako Railway was merged into the Musashino Railway, one of the corporate ancestors of today's Seibu Railway, and the line passed out of independent ownership. Even after the merger the route long retained its original 600 V DC electrification, unlike Seibu's other 1,500 V lines. Yasaka Station opened on 1 October 1942, and in the post-war years the line's stations were repeatedly renamed: the reservoir-side terminus, earlier called Sayama-kōen-mae, was renamed Tamako on 1 September 1951.

The line's electrification was finally brought up to Seibu standard in stages during the 1950s and early 1960s. The Kodaira–Hagiyama section was raised to 1,500 V on 18 March 1955, and the Hagiyama–Tamako section on 16 September 1958, the latter change accompanying a rearrangement of Hagiyama Station and the start of through services from the Shinjuku Line to Tamako. After Tamako Station was relocated about 0.4 kilometres on 20 September 1961, the remaining Kokubunji–Hagiyama section was raised to 1,500 V on 21 September 1961, completing line-wide conversion. The following year, on 1 September 1962, the Kodaira–Hagiyama stretch was transferred to the Jōsui Line, today's Seibu Haijima Line.

From the outset the line south of Hagiyama was heavily reworked, with stations opened, closed, moved and renamed many times; at its most crowded, between 1939 and early 1953, eight stations were packed into the 4.4-kilometre southern section. Successive closures and the 1966 merger of Hitotsubashi University and Kodaira-gakuen stations into the present Hitotsubashi-Gakuen station left only a handful of stops, and of the original 1928 stations on this stretch only Ōmekaidō survives unmoved. At Kokubunji, where the platform had been too short for 20-metre cars, the Tamako Line platform was rebuilt in June 1990; the operating distance was shortened by 0.1 kilometre and full-size 20-metre trains were introduced between Kokubunji and Hagiyama.

In its modern role the line is primarily a local commuter service, while together with the connecting Seibu Yamaguchi Line it also carries visitors to Seibuen Amusement Park and crowds to the Seibu Dome. One-man operation began on the Kokubunji–Hagiyama section in August 1998 and was extended to the whole line on 16 March 2013, when the line's express trains were discontinued. On 22 August 2016, Typhoon No. 9 caused a slope failure between Musashi-Yamato and the then Seibu-yūenchi station that derailed a four-car train; no one was injured, the affected section was suspended, and service resumed on 6 September 2016. Four-door 9000 series one-man trains entered service on 1 October 2020, and on 13 March 2021 Seibu-yūenchi station was renamed Tamako, restoring the name the terminus had carried until 1979.

• 192510 October: a railway licence is granted to Hakone Land for a line through Kitatama District (Kokubunji–Higashimurayama).
• 192815 January: the Tamako Railway Company is incorporated; on 6 April it opens the Tamako Line's first segment, Kokubunji–Hagiyama (4.4 km); on 2 November it opens the 1.0 km Kodaira Line, Hagiyama–Hon-Kodaira.
• 193023 January: the line is extended 3.6 km from Hagiyama to a temporary Murayama-chōsuichi station; on 7 May the Kokubunji–Murayama-chōsuichi route is electrified at 600 V DC.
• 193412 April: steam haulage is abolished between Kokubunji and Hagiyama.
• 193630 December: the final 0.9 km section to Murayama-chōsuichi station opens, completing the line; the temporary station is renamed Musashi-Yamato and moved to its present site.
• 194012 March: the Tamako Railway is merged into the Musashino Railway, a corporate ancestor of Seibu Railway.
• 19421 October: Yasaka Station opens; in the post-war years the reservoir-side terminus, formerly Sayama-kōen-mae, is renamed Tamako (1 September 1951).
• 195518 March: the Kodaira–Hagiyama section is raised to 1,500 V; on 16 September 1958 the Hagiyama–Tamako section follows, accompanied by a rearrangement of Hagiyama Station and the start of through services from the Shinjuku Line to Tamako.
• 196120 September: Tamako Station is relocated about 0.4 km; on 21 September the Kokubunji–Hagiyama section is raised to 1,500 V, completing line-wide conversion.
• 19621 September: the Kodaira–Hagiyama section is transferred to the Jōsui Line, today's Seibu Haijima Line.
• 19661 July: Hitotsubashi University and Kodaira-gakuen stations are merged into the present Hitotsubashi-Gakuen station.
• 199024 June: with the rebuilding of Kokubunji Station, the operating distance is shortened by 0.1 km and 20-metre cars are introduced between Kokubunji and Hagiyama.
• 199821 August: one-man operation begins on the Kokubunji–Hagiyama section.
• 201316 March: one-man operation is extended to the whole line and the line's express trains are discontinued.
• 201622 August: Typhoon No. 9 causes a slope failure between Musashi-Yamato and Seibu-yūenchi that derails a four-car train (no injuries); the section is suspended and reopens on 6 September.
• 20201 October: four-door 9000 series one-man trains enter service; on 13 March 2021 Seibu-yūenchi station is renamed Tamako, restoring the name the terminus had held until 1979.