Tōhoku Main Line

The line was not built by the state but by Nippon Railway, Japan's first private railway company, whose project to link Tokyo with Aomori in the far north grew out of proposals put to the government in the early 1870s and a peerage-led railway-building movement around 1880. Construction proceeded region by region. The first segment, between Ueno and Kumagaya, opened on 28 July 1883 as Japan's first privately run railway. The line was extended to Utsunomiya in 1885, though at first the Tone River had to be crossed by ferry; once the Tone River Bridge was completed in 1886, Ueno and Utsunomiya were directly connected. The railway then pushed steadily north through Kōriyama, Sendai and Ichinoseki, reaching Morioka by 1890.

On 1 September 1891 the segment between Morioka and Aomori opened, completing the through route from Ueno to Aomori and creating what was then the longest continuous railway line in Japan; the first through services ran just once each way per day and took about twenty-six and a half hours. At this stage the route was known as the Nippon Railway Ōshū Line; the name "Tōhoku Main Line" was not adopted until 1909, after the railway had passed into state hands. Nippon Railway was nationalised on 1 November 1906 under the Railway Nationalization Act, and the line thereafter became a trunk route of the government railways.

When Tokyo Station opened in 1925, the line was extended south from Ueno to the new terminus, and for decades trains ran through between the Tōkaidō and Tōhoku main lines via this section. Electrification advanced in stages from the capital outward: the short Tokyo–Tabata stretch was electrified at 1,500 V DC in 1909, reaching Akabane in 1928, Ōmiya in 1932 and Kuroiso in 1959. North of Kuroiso the line used 20 kV AC, reaching Fukushima in 1960, Sendai in 1961, Morioka in 1965 and finally Aomori in 1968, by which point the whole Tokyo–Aomori route was electrified and largely double-tracked. That milestone was marked by the sweeping nationwide "Yonsantō" timetable revision of October 1968, which greatly expanded the line's express services.

The opening of the Tōhoku Shinkansen in 1982 reshaped the line's role. Long-distance limited expresses migrated to the high-speed line, and the spare capacity that opened up was used to run more medium-distance local trains. The Shinkansen, which largely parallels the older route, also took over land once occupied by the line's intercity tracks. In 1990 the Ueno–Kuroiso section was given the service name "Utsunomiya Line," and passengers increasingly stopped calling that stretch the Tōhoku Main Line at all.

The Shinkansen's northward extension then carved away the line's far north. When it reached Hachinohe on 1 December 2002, the parallel conventional track from Morioka to Metoki passed to the third-sector IGR Iwate Galaxy Railway and the Metoki–Hachinohe section to the Aoimori Railway; the Tōhoku Main Line was left in two pieces, and its operating length fell to 631.3 km, then the second-longest conventional line in Japan after the San'in Main Line. With the further extension to Shin-Aomori on 4 December 2010, the remaining Hachinohe–Aomori section also passed to the Aoimori Railway, the name "Tōhoku Main Line" vanished from Aomori Prefecture, and the line shrank to its present 535.3 km — third among Japan's conventional lines, after the San'in and Tōkaidō main lines.

Today the Tōhoku Main Line officially runs only from Tokyo to Morioka, and in everyday usage the name is applied mainly to the Kuroiso–Morioka portion, the Tokyo–Kuroiso section being known as the Utsunomiya Line. Because electrification changes from DC to AC at Kuroiso, no regularly scheduled passenger trains run through that station, and no single service covers the whole line. After the 2015 opening of the Ueno–Tokyo Line restored through commuter running at its southern end, the corridor now carries dense suburban and regional services together with heavy JR Freight traffic linking the Tokyo region with northern Honshū and Hokkaidō.

• 188328 July: Nippon Railway opens the first segment, Ueno–Kumagaya, as Japan's first privately run railway.
• 1885The line is extended to Utsunomiya; the Tone River initially has to be crossed by ferry.
• 188617 June: the Tone River Bridge is completed, directly connecting Ueno and Utsunomiya.
• 1887December: the line reaches the Sendai area, opening Kōriyama to the Shiogama area via Fukushima and Sendai.
• 1890The line is extended north to Morioka (Ichinoseki–Morioka opens 1 November).
• 18911 September: the Morioka–Aomori segment opens, completing the Ueno–Aomori through route — then the longest continuous railway line in Japan; first through trains run once daily, ~26.5 hours one way.
• 19061 November: Nippon Railway is nationalised under the Railway Nationalization Act; the line becomes a government trunk route.
• 1909The route, until then the Nippon Railway Ōshū Line, is renamed the Tōhoku Main Line; the Tokyo–Tabata section is electrified at 1,500 V DC.
• 19251 November: Tokyo Station becomes the line's southern terminus; the Tōhoku Main Line is extended from Ueno to Tokyo.
• 1959DC electrification (1,500 V), having reached Akabane in 1928 and Ōmiya in 1932, is extended to Kuroiso.
• 196822 August: AC electrification (20 kV) reaches Aomori, completing electrification of the whole Tokyo–Aomori route; the nationwide 'Yonsantō' timetable revision follows in October.
• 1982The Tōhoku Shinkansen opens; long-distance limited expresses shift to it, while the freed capacity is used for more medium-distance local trains on the conventional line.
• 199010 March: the Ueno–Kuroiso section is given the service name 'Utsunomiya Line'.
• 20021 December: with the Shinkansen extended to Hachinohe, Morioka–Metoki passes to the IGR Iwate Galaxy Railway and Metoki–Hachinohe to the Aoimori Railway; the line falls to 631.3 km, then the second-longest conventional line after the San'in Main Line.
• 20104 December: with the Shinkansen extended to Shin-Aomori, Hachinohe–Aomori passes to the Aoimori Railway; the name 'Tōhoku Main Line' disappears from Aomori Prefecture and the line is reduced to 535.3 km, third-longest after the San'in and Tōkaidō main lines.
• 2015The Ueno–Tokyo Line opens, restoring through commuter running between Tokyo and Ueno over the line's southern end.