Hachikō Line

The route was planned as a state project. It was listed as a projected line in Schedule No. 51 of the amended Railway Construction Act as a railway 'from Hachiōji in Tokyo Prefecture via Hannō in Saitama Prefecture to Takasaki in Gunma Prefecture.' The private Tōbu Railway had also conceived a line over the same corridor, but once the Railway Ministry took the Hachikō Line up as its own direct undertaking, Tōbu abandoned its plans, including any extension beyond Takasaki. The line was therefore built from the outset by the national railway, not bought in from a private operator, and was constructed from both ends at once.

Construction began simultaneously from the north and the south. The Hachikō North Line opened first, from Kuragano to Kodama, on 1 July 1931, and the Hachikō South Line followed from Hachiōji to Higashi-Hannō on 10 December 1931. The two lines were then extended toward each other in stages: the North Line reached Yorii from Kodama on 25 January 1933, while the South Line was pushed from Higashi-Hannō to Ogose on 15 April 1933 and on to Ogawamachi on 24 March 1934.

The final gap, from Ogawamachi to Yorii, opened on 6 October 1934, joining the northern and southern halves into a single through route. On that date the South Line was renamed and the North Line absorbed into it, and the whole Hachiōji–Kuragano route became the Hachikō Line. The line skirted the foothills west of the metropolis, linking the silk-trading and market towns along the edge of the plain and connecting the Chūō, Kawagoe, Tōbu Tōjō, Chichibu and Takasaki lines that crossed it.

The line is remembered for two of the deadliest railway accidents in modern Japanese history, both in the early postwar years. On 24 August 1945, nine days after the end of the Pacific War and during heavy rain, two trains collided head-on on the Tama River bridge, killing at least 105 people. Less than two years later, on 25 February 1947, an overcrowded train derailed and overturned, with 184 fatalities — described as Japan's worst rail accident since the Second World War in terms of lives lost.

Postwar modernisation came gradually. Steam haulage of passenger services ended on 20 November 1958, when operation switched to electric trains on the part of the line that was wired, and centralised traffic control was commissioned over the whole route on 27 February 1985. Under the privatisation and break-up of Japanese National Railways, the line passed to JR East on 1 April 1987.

The defining modern change came on 16 March 1996, when the southern Hachiōji–Komagawa section was electrified at 1,500 V DC. From that day the line was split into separate northern and southern operating patterns at Komagawa: southern trains began through-running over the Kawagoe Line to Kawagoe, while the non-electrified Komagawa–Takasaki section was given over entirely to KiHa 110 series diesel railcars with one-man operation. The two-character split between an electrified commuter south and a diesel rural north has defined the line ever since; later changes extended one-man operation to the southern electric trains in 2022 and ended single-car running north of Komagawa in 2025.

• 19311 July: the Hachikō North Line opens between Kuragano and Kodama.
• 193110 December: the Hachikō South Line opens between Hachiōji and Higashi-Hannō.
• 193325 January: the Hachikō North Line is extended from Kodama to Yorii.
• 193315 April: the Hachikō South Line is extended from Higashi-Hannō to Ogose.
• 193424 March: the Hachikō South Line is extended from Ogose to Ogawamachi.
• 19346 October: the final Ogawamachi–Yorii section opens, connecting the two halves; the South Line is renamed and the North Line absorbed into it, and the whole Hachiōji–Kuragano route becomes the Hachikō Line.
• 194524 August: nine days after the end of the Pacific War, two trains collide head-on on the Tama River bridge in heavy rain, killing at least 105 people.
• 194725 February: an overcrowded train derails and overturns, killing 184 people — Japan's worst rail accident since the Second World War in terms of fatalities.
• 195820 November: steam haulage of passenger services ends, with operation switching to electric trains on the wired portion of the line.
• 198527 February: centralised traffic control (CTC) is commissioned over the whole line.
• 19871 April: under the privatisation and break-up of Japanese National Railways, the line passes to JR East.
• 199616 March: the southern Hachiōji–Komagawa section is electrified at 1,500 V DC; operations are split north and south at Komagawa, southern trains begin through-running to Kawagoe over the Kawagoe Line, and the non-electrified Komagawa–Takasaki section is given over entirely to KiHa 110 series diesel railcars with one-man operation.
• 202212 March: one-man operation is introduced on the southern electric services.
• 202515 March: single-car services between Komagawa and Takasaki are discontinued.