Sagami Railway Co., Ltd.

The railway descends from two companies founded in December 1917. The original Sagami Railway, planned as a north–south link between the Tōkaidō and Chūō lines, held its founding meeting on 18 December 1917 and was established at Chigasaki on 4 January 1918; it opened Chigasaki–Samukawa on 28 October 1921 and completed its line to Hashimoto on 29 April 1931. Sagami River gravel was its second pillar, at times out-earning passenger traffic — hence the taunt 'gravel railway'. The Jinchū Railway, established on 15 December 1917 by local notables of Seya village, built today's main line: Futamata-gawa–Atsugi opened on 12 May 1926, connected with the Sagami Railway at Atsugi that July, and reached Yokohama Station on 27 December 1933. Both companies struggled and fell into the orbit of the Tōkyō Yokohama Electric Railway, forerunner of Tōkyū — Jinchū in September 1939, the Sagami Railway in June 1941. In November 1941 the old route into Atsugi became the freight-only Atsugi Line and one-way through running began onto the Odakyū line, lasting until 1964.

The two merged in April 1943, the Sagami Railway absorbing the Jinchū Railway and renaming the routes the Sagami Line and the Jinchū Line. In June 1944 the Sagami Line and its Nishi-Samukawa branch were nationalized in wartime to serve as a bypass between the Tōkaidō and Chūō main lines; the route never returned and is today JR East's Sagami Line. Only the former Jinchū section remained, its traffic surging with the opening of the Atsugi naval airfield. The main line was fully electrified by September 1944; from June 1945 to May 1947 the whole railway business was entrusted to the parent Tōkyū. In June 1947 Kawamata Teijirō and fellow officers bought Tōkyū's roughly 70 percent holding, restoring independence.

In 1951 Tōkyū's Gotō Keita mounted a takeover through Odakyū Electric Railway, the prize being the land at Yokohama Station's west exit. A capital-doubling resolution narrowly passed at a 6 September 1951 extraordinary shareholders' meeting blocked the bid, and the Fair Trade Commission ordered the accumulated shares released on 12 September, though Odakyū remained largest shareholder until 2021. In 1952 the company bought 24,688 square metres at the west exit from the Standard Vacuum Oil Company; developed into Yokohama Takashimaya, Sōtetsu Joinus and the Diamond underground mall, it became an earnings source exceeding the railway itself. The main line was double-tracked in stages between November 1951 and March 1974, and the Izumino Line opened to Izumino in April 1976. With its extension to Izumi-chūō in April 1990 the company met the Japan Private Railway Association's criteria and was formally recognized as a major private railway on 31 May 1990.

From the late 1990s the group spun off its bus, real-estate and other arms, and on 16 September 2009 the old Sagami Railway renamed itself Sōtetsu Holdings while the railway passed to the present Sagami Railway Co., Ltd. — strictly a different legal entity, incorporated on 24 November 1964 as KK Ōzeki Shuzō and dormant by 2009. It ran its first Limited Express on 27 April 2014, until then the only major private railway without one, and on 24 March 2016 it left the gravel business that had sustained it for 97 years. From 2016 the fleet began repainting in 'YOKOHAMA NAVYBLUE', and in 2019 the 20000 series, built for the Tōkyū through services, won the company's first Laurel Prize.

Apart from the one-way Odakyū service ended in 1964, Sōtetsu had never run through services with another operator. On 30 November 2019 the Sōtetsu Shin-yokohama Line opened from Nishiya to Hazawa yokohama-kokudai and through services with JR East began over the Tōkaidō freight line as the Sōtetsu–JR Link Line — the company's first mutual through-running, taking Sōtetsu cars via the Saikyō Line into Tokyo. On 18 March 2023 the line reached Shin-yokohama, meeting the new Tōkyū Shin-yokohama Line; the Sōtetsu–Tōkyū Link Line opened through services with Tōkyū, Tokyo Metro, the Toei Subway, Saitama Rapid Railway and Tōbu Railway — the company's first running onto subway lines and its first scheduled own-car operation in Saitama Prefecture. The Shin-yokohama Line was built and is owned by the Japan Railway Construction, Transport and Technology Agency, with operation commissioned to Sōtetsu.

• 191718 December: the original Sagami Railway held its founding general meeting (the company was formally established at Chigasaki on 4 January 1918). The Jinchū Railway, which built today's main line, had held its own founding meeting on 2 December and was established as the Jinchū Tramway on 15 December 1917.
• 192128 October: the Sagami Railway opened its first section, Chigasaki–Samukawa, part of what is now JR East's Sagami Line.
• 192612 May: the Jinchū Railway opened Futamata-gawa–Atsugi, the first section of today's Sōtetsu Main Line; on 15 July the Sagami Railway reached Atsugi and the two railways connected there.
• 193327 December: after years of piecemeal extensions, the Jinchū Railway finally reached Yokohama Station.
• 1943April: the Sagami Railway absorbed the Jinchū Railway, both then being in the Tōkyū group; the two routes became the Sagami Railway's Sagami Line and Jinchū Line.
• 1944June: the Sagami Line (Chigasaki–Hashimoto) and the Nishi-Samukawa branch were nationalized as a wartime bypass between the Tōkaidō and Chūō main lines — today's JR Sagami Line — leaving only the former Jinchū section with the company. In September the whole main line was electrified.
• 1947June: Kawamata Teijirō and fellow officers acquired the roughly 70 percent of the company's shares held by Tōkyū and made the company independent; the entire railway business had been entrusted to Tōkyū from June 1945 to May 1947.
• 19516 September: an extraordinary shareholders' meeting narrowly approved a doubling of capital, blocking the takeover that Tōkyū's Gotō Keita had mounted through Odakyū Electric Railway; on 12 September the Fair Trade Commission ruled that Odakyū must release the shares it had accumulated.
• 1952The company purchased 24,688 square metres of land at Yokohama Station's west exit from the Standard Vacuum Oil Company; its development — later the site of Yokohama Takashimaya, Sōtetsu Joinus and the Diamond underground mall — grew into an earnings source exceeding the railway business itself.
• 1976April: the Izumino Line opened from Futamata-gawa to Izumino.
• 1990April: the Izumino Line was extended to Izumi-chūō; with the major-railway requirements met, the company was formally recognized as a major private railway by the Japan Private Railway Association on 31 May.
• 200916 September: in the group's move to a holding-company structure, the former Sagami Railway was renamed Sōtetsu Holdings and the railway business was inherited by the present Sagami Railway Co., Ltd. — a dormant subsidiary incorporated on 24 November 1964 as KK Ōzeki Shuzō and renamed Sōtetsu Junbi Kaisha on 22 January 2009.
• 201930 November: the Sōtetsu Shin-yokohama Line opened from Nishiya to Hazawa yokohama-kokudai, and through services with JR East began over the Tōkaidō freight line as the Sōtetsu–JR Link Line — the company's first mutual through-running, taking Sōtetsu cars via the Saikyō Line into Tokyo.
• 202318 March: the Shin-yokohama Line was extended to Shin-yokohama, connecting with the simultaneously opened Tōkyū Shin-yokohama Line; through services began with Tōkyū, Tokyo Metro, the Toei Subway, Saitama Rapid Railway and Tōbu Railway as the Sōtetsu–Tōkyū Link Line — the company's first running onto subway lines and the first scheduled operation of its own cars in Saitama Prefecture. The same year the lines were formally renamed the Sōtetsu Main Line and Sōtetsu Izumino Line.