Nagano Line

The line was assembled from several earlier private railways. Its oldest part began as a project of the Kawatō Railway (Katō Tetsudō), which had taken over a licence first granted to the Saku Railway in 1920 for a line between Yashiro and Suzaka, and obtained further licences in 1921 for extensions toward Kijima and from Shinshu-Nakano on to Yudanaka and Shibu-Yasudai. The first section to carry trains, between Suzaka and Shinshu-Nakano, opened on 26 March 1923, bringing the stations of Toyosu (the present Kita-Suzaka), Obuse, Entoku and Shinshu-Nakano into service. The Kawatō Railway electrified its whole line on 29 January 1926.

A second company, the Nagano Electric Railway (Nagano Denki Tetsudō), opened the stretch between Gondō and Suzaka on 28 June 1926, adding Gondō, Zenkoji-shita, Hongō, Kirihara, Yoshidamachi (now Shinano-Yoshida), Asahi, Yanagihara, Murayama and Hino; the Gondō–Yoshidamachi portion was built as double track. On 30 September 1926 the Kawatō Railway absorbed the Nagano Electric Railway and renamed itself Nagano Dentetsu, the company that still runs the line today. At that point the Suzaka–Shinshu-Nakano section formed part of the Kawatō Line, while the newly opened Gondō–Suzaka section was called the Nagano Line.

The mountain end of the route opened on 28 April 1927, when the Shinshu-Nakano–Yudanaka section was completed as the Heion Line, serving Nakano-Matsukawa, Takehara (now Shinano-Takehara), Yomase, Kamijō and Yudanaka; this section was renamed the Yamanouchi Line on 27 August 1927. The final link, a double-track section from Nagano Station to Gondō, opened on 24 June 1928, completing through running between Nagano and Yudanaka and opening Nagano (Nagaden), Nishikichō (now Shiyakusho-mae) and Midorichō. The licensed extension beyond Yudanaka toward Shibu-Yasudai was never built and was formally cancelled in 1931.

In the post-war decades the line developed a distinctive limited-express service. The 2000 series entered service on 15 March 1957, inaugurating the named limited expresses Shirane, Yokote, Shiga, Kasadake and Iwasuge; these were later consolidated into the single "Okushiga" limited express. In 1966 the line introduced the 0 series "OS Car" commuter trains. Freight traffic, once significant — including a dedicated apple-shipping train that ran from Shinshu-Nakano toward Osaka from 1962 — was wound down, with freight on the Nagano Line abolished on 1 September 1970 and across the whole Nagaden network by 1 April 1979.

On 1 March 1981 the Nagano–Zenkoji-shita section was rebuilt as a grade-separated underground line through central Nagano, and Nishikichō Station was renamed Shiyakusho-mae. Centralised traffic control had been commissioned between Yudanaka and Asahi in 1980 and was extended to Nagano in 1984. For decades the route still carried three separate names — Nagano Line, Kawatō Line and Yamanouchi Line — until 18 September 2002, when the Suzaka–Shinshu-Nakano portion of the Kawatō Line and the Yamanouchi Line were combined with the existing Nagano–Yudanaka services and the whole Nagano–Yudanaka route was renamed simply the Nagano Line.

The twenty-first century brought new rolling stock and tourism-oriented services. The 1000 series "Yukemuri", rebuilt from former Odakyū 10000 series "Romancecar" vehicles, entered service on 9 December 2006, and the 2100 series "Snow Monkey", converted from former JR East 253 series "Narita Express" stock, began running on 26 February 2011, the same revision from which the long-serving 2000 series left regular duty. The line continues to mix high-frequency local trains around Nagano with limited expresses to Yudanaka. On 1 December 2025 its operating length was adjusted from 33.2 to 33.1 kilometres alongside a fare revision, and the operator has announced that nationwide IC cards such as Suica are due to become usable across the whole line from the spring of 2027.

• 19203 May: a licence for a Yashiro–Suzaka line is granted to the Saku Railway; it is transferred to the Kawatō Railway on 6 September.
• 192126 May: the Kawatō Railway is licensed for the Suzaka–Kijima and Shinshu-Nakano–Yudanaka–Shibu-Yasudai sections.
• 192326 March: the Kawatō Railway opens the first section, Suzaka–Shinshu-Nakano (with Toyosu — now Kita-Suzaka — Obuse, Entoku and Shinshu-Nakano).
• 192629 January: the Kawatō Railway electrifies its whole line. 28 June: the Nagano Electric Railway opens Gondō–Suzaka (Gondō–Yoshidamachi double-track). 30 September: the Kawatō Railway absorbs the Nagano Electric Railway and is renamed Nagano Dentetsu; the Gondō–Suzaka section becomes the Nagano Line.
• 192728 April: the Shinshu-Nakano–Yudanaka section opens as the Heion Line (with Nakano-Matsukawa, Takehara — now Shinano-Takehara — Yomase, Kamijō and Yudanaka); it is renamed the Yamanouchi Line on 27 August.
• 192824 June: the double-track Nagano–Gondō section opens, completing through running between Nagano and Yudanaka (with Nagano (Nagaden), Nishikichō — now Shiyakusho-mae — and Midorichō).
• 193110 July: the licence for the unbuilt Yudanaka–Shibu-Yasudai extension is cancelled.
• 195715 March: the 2000 series enters service; the limited expresses Shirane, Yokote, Shiga, Kasadake and Iwasuge begin operating.
• 196624 November: the 0 series "OS Car" commuter trains enter service.
• 19701 September: freight operations on the Nagano Line are fully abolished (freight across the whole Nagaden network ends on 1 April 1979).
• 19811 March: the Nagano–Zenkoji-shita section is grade-separated and put underground; Nishikichō Station is renamed Shiyakusho-mae.
• 1984CTC signalling, commissioned between Yudanaka and Asahi in 1980, is extended to Nagano.
• 200218 September: the Suzaka–Shinshu-Nakano part of the Kawatō Line and the Yamanouchi Line are merged with the Nagano–Yudanaka services, and the whole Nagano–Yudanaka route is renamed the Nagano Line.
• 20069 December: the 1000 series "Yukemuri", rebuilt from former Odakyū 10000 series "Romancecar" stock, enters service.
• 201126 February: the 2100 series "Snow Monkey", converted from former JR East 253 series "Narita Express" stock, enters service; the 2000 series leaves regular service.
• 20251 December: the line's operating length is adjusted from 33.2 km to 33.1 km in conjunction with a fare revision.