The Sobu Main Line (総武本線) is a main line run by East Japan Railway Company (JR East) from Tokyo Station in Chiyoda, Tokyo, to Choshi Station in Choshi, Chiba Prefecture. It also has a branch from Kinshicho station to Ochanomizu.
History
In 1872 Japan's first railway opened. In 1884 the Nippon Railway ran a private line from Ueno to Takasaki with good results, and a national boom in private railways followed. In Chiba Prefecture the first plans were for horse-drawn railways, but from about 1886 steam railway plans were put forward. In November 1887 the Buso Railway (武総鉄道) and the Soshu Railway (総州鉄道) both applied. Chiba's governor was cautious about railways, and both applications were rejected. In January 1889 the two groups merged and founded the Sobu Railway Company (総武鉄道株式会社). The name Sobu reversed the rejected name Buso. In February 1889 the company applied again for a route from Honjo in Tokyo through Ichikawa, Funabashi, Chiba, Sakura and Yachimata. The route passed army base towns to win army support, and the stated purpose was military transport and transport to government reclaimed land.
In April 1889 the company received a provisional permit, and in December 1889 a licence for the Koiwa to Sakura section. Work began in August 1893 after some changes to the plan. The Railway Construction Act of 1892 had named a future line from Ueno through Chiba and Sakura to Choshi. On 20 July 1894 the Ichikawa to Sakura section opened, the first railway in Chiba Prefecture. Japan and China declared war on 1 August 1894, and the line was used to move troops. On 9 December 1894 the line reached Honjo, crossing the Edo River. On 1 May 1897 it was extended to Narito, and on 1 June 1897 to Choshi. The line also linked with the Narita Railway at Sakura.
On 5 April 1904 the line reached Ryogokubashi (now Ryogoku), which became the terminal on the city side. Passengers there used the city tram lines, and goods were sent by river boat on the Sumida. In 1912 the Keisei Electric Railway opened its first section and competed with the line on the Tokyo, Funabashi and Chiba route. On 1 September 1907 the line was bought and nationalised under the Railway Nationalisation Act (鉄道国有法). On 12 October 1909 it was named the Sobu Main Line under the national railway naming rules. On 1 May 1915 Honjo station was renamed Kinshicho. On 1 September 1923 the Kanto earthquake killed many people around Ryogoku. Afterwards a freight branch to Shin-Koiwa and Kanamachi opened in 1926, and a branch from Kameido to Konagawa opened in 1929. On 1 October 1931 Ryogokubashi station was renamed Ryogoku.
On 1 July 1932 the line was extended from Ryogoku to Ochanomizu, with electric trains running on the new section. This linked the Sobu line with other national railway lines in central Tokyo. In March 1932 the Railway Ministry approved electrification from Ryogoku to Ichikawa. Electric trains ran on that section from 15 March 1933. From 15 September 1933 the Ichikawa to Funabashi section was electrified, and electric local trains ran through to Nakano on the Chuo Line. On 1 July 1935 the Funabashi to Chiba section was electrified. From then on the line was split at Chiba: commuter electric trains ran west toward Ochanomizu, and steam-hauled passenger trains ran east toward Choshi. In the war, on 10 March 1945 a US air raid on Tokyo killed about one hundred thousand people, and many victims went to Ryogoku, Kinshicho and Kameido stations. The army expected a US landing at Kujukuri beach, and used the line for large troop movements under the Ketsugo plan. Japan accepted the Potsdam Declaration on 15 August 1945, so large-scale fighting along the line was avoided.
After the war the line was in poor shape, and traffic grew fast. The line was double-track and electrified only from Chiba westward; east of Chiba it was single-track and not electrified. The 1964 five-direction commuter plan (通勤五方面作戦) led to a decision to build a Tokyo to Chiba express track, including a new Tokyo to Kinshicho line. In December 1967 a government decision said that quadruple tracking from Tokyo to Chiba should progress before the Narita airport opened, planned for 1971. On 28 March 1968 the Chiba to Sakura section was electrified, along with the Sakura to Narita section of the Narita Line. On 13 July 1968 the Chiba to Kisarazu section followed. In 1969 the Tozai Line reached Nishi-Funabashi, which reduced the load on the commuter Sobu line. On 4 June 1972 the Shin-Koiwa to Tsudanuma section was made quadruple track, and on 15 July 1972 the line was extended from Tokyo to Kinshicho, making Tokyo station the new start of the line. Ryogoku's importance fell sharply. On 1 October 1980 through running with the Yokosuka Line began. On 26 October 1974 the Sakura to Choshi section was electrified, completing the electrification of the main line. In 1978 Narita Airport opened, and the Sobu and Narita lines gave rail access to it. In 1981 the quadruple track reached Chiba. In 1987 the line was split up as part of the national railway breakup.
On 1 April 1987 the passenger service and track passed to East Japan Railway Company (JR East), and the freight section from Shin-Koiwa Sogo to Narito passed to Japan Freight Railway Company (JR Freight). On 25 March 1990 ATS-P safety signalling started on the local tracks from Ochanomizu to Chiba, and it was extended from Kinshicho to Ichikawa on 24 October 1993, from Ichikawa to Chiba on 31 October 1993, and from Chiba to Sakura on 28 October 1994. The Keiyo Line (京葉線) opened its first section in 1986 and reached Tokyo station in 1990. Some express trains moved to it, which eased the fast tracks of the Sobu line. In 1991 the Narita Express began serving Narita Airport. In May 1999 the ATOS train management system was introduced on the local tracks from Ochanomizu to Chiba, and on 30 September 2000 between Tokyo and Makuhari. In 2000 a transport council report recommended a new line from Shin-Urayasu through Funabashi to Tsudanuma by 2015. JR East had not formally announced the plan.
In December 2005 Series E257 500 番台 express trains replaced the 183 and 189 series on Sobu express services. On 21 October 2006 the 211 series 3000 番台 entered service. In March 2009 the Chiba to Choshi section joined the Tokyo commuter area, and the Suica card began to be used. On 1 October 2009 4-door 209 series 2000 and 2100 番台 trains began running between Chiba and Choshi, as the 113 series was ageing. On 12 March 2010 the parcel trains were withdrawn. In 2011 Shin-Koiwa Sogo station was renamed Shin-Koiwa signal station. On 16 February 2020 ATOS was introduced at the Chiba station platforms for the Uchibo, Sotobo, Sobu and Narita lines. On 1 July 2026 management of the line moved to business divisions, with the Chiba division taking the section from Chiba to Choshi. On 13 August 2026 heavy rain stopped services between Sakura and Narito. On 21 September 2026 heavy rain from Typhoon No. 25 washed away the track bed between Enoto and Narito, and the line was expected to be closed for at least 1 month. Services resumed between Enoto and Yachimata on 27 September 2026, and buses replaced trains between Yachimata and Narito from 28 September 2026.
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Written by an AI from the line's history on Japanese Wikipedia, nothing else, and checked by a program for dates and numbers that are not in those facts. It can still be wrong. Adapted from Japanese Wikipedia, CC BY-SA 4.0; this text is shared under the same licence.