Looking from Musashi-Itsukaichi Station towards Musashi-Masuko Station
The Itsukaichi Line was built by the Itsukaichi Railway in 1925. In 1930, all sections (Tachikawa - Haijima - Musashi-Itsukaichi - Musashi-Iwai) were opened. There were two competing railways between Tachikawa and Haijima: the Ōme Electric Railway (now the Ōme Line) and the Itsukaichi Railway. In 1940, the Itsukaichi Railway was taken over by the Nambu Railway, becoming the Nambu Railway Itsukaichi Line. In 1944, Nambu Railway was nationalized and this line became the JGR Itsukaichi Line. At the same time, the section of the line between Tachikawa and Haijima was deemed non-essential and closed. However, the Tachikawa - Musashi-Uenohara and Musahi-Uenohara - Nishi-Tachikawa sections of the former Nambu Railway are still used by Chūō Main Line and Nambu Line trains traveling to and from the southern area of Tachikawa Station.
8 December 1931: Musashi-Tanaka - Haijima-Tamagawa freight branch (1.6 km) opens; Haijima-Tamagawa Station (freight only) opens. Tamagawa Station is renamed Musashi-Tamagawa Station.
3 October 1940: Line taken over by Nambu Railway, becomes Itsukaichi Line. Musashi-Tamagawa Station closes.
1 April 1944: Line is nationalized. Byōinmae Station renamed Musashi-Hikita Station. Musashi-Uenohara, Miyazawa, and Musashi-Tanaka stations close. Origin of freight branch (Musashi-Tanama - Haijima-Tamagawa) moved to Minami-Haijima Station (+1.4 km). Distance between Musashi-Itsukaichi and Musashi-Iwai shortened by 0.1 km.
11 October 1944: Tachikawa - Haijima section of Main Line and Minami-Haijima - Haijima-Tamagawa section of freight branch close. Gouchi, Musashi-Fukushima, Minami-Nakagami, Ōgami, Minami-Haijima, Haijima-Tamagawa stations close.
17 February 1961: Haijima - Musashi-Iwai section electrified at 1,500 V DC.
1 February 1971: Ōkuno - Musashi-Iwai section of main line closes. Passenger service between Musashi-Itsukaichi and Ōkuno ceases; section becomes a freight branch. CTC installed in all sections.
15 November 1982: Musashi-Itsukaichi - Ōkuno freight branch closes; all freight services discontinued.
31 March 1987: Nishi-Akiru Station renamed Akigawa Station.
1 April 1987: Following privatization of JNR line becomes part of JR East.