Keikyu Corporation

The railway then grew along the Tōkaidō corridor: services between Ōmori and Kawasaki began in February 1901, the Kamata–Anamori branch — ancestor of today's Airport Line — opened in June 1902, and Kawasaki–Kanagawa followed in December 1905, while a side business supplied electric light and power from 1901 until 1923. In March 1904 the whole line was regauged from standard gauge to the 1,372-mm "horse-tram" gauge with an eye to through-running onto the Tokyo City Tram. Construction then carried the railway into Tokyo and down the peninsula: Takanawa–Shinagawa opened in March 1925; the Shōnan Electric Railway opened its standard-gauge Kōganechō–Uraga line and Kanazawa-Hakkei–Shōnan Zushi branch on 1 April 1930; and on 26 December 1931 the two systems were joined at Hinodechō, allowing Yokohama–Uraga through service. On 1 April 1933 Keihin closed Takanawa station, brought its trains into Shinagawa Station, and converted its entire line back to standard gauge, beginning Shinagawa–Uraga through-running. The company had also opened Japan's first toll-road business, between Ōfuna and Katase, in July 1931. In March 1939 its largest shareholding passed to Tokyo Rapid Railway, drawing Keihin and Shōnan effectively into the orbit of Tōkyō Yokohama Electric Railway, and on 1 November 1941 Keihin absorbed Shōnan Electric Railway.

On 1 May 1942, under the wartime Land Transport Business Coordination Act, Keihin was merged together with Odakyū into Tōkyō Yokohama Electric Railway, creating Tokyo Kyūkō Electric Railway — the "Dai-Tōkyū" combine. The war years nevertheless extended the network, with the Kurihama Line opening from Yokosuka-Horinouchi (now Horinouchi) to Kurihama on 1 December 1942 and the Daishi Line being extended in stages in 1944–45. On 1 June 1948 the present company, Keihin Kyūkō Dentetsu (then rendered in English as Keihin Electric Express Railway), was established as one of three companies — alongside Odakyū Electric Railway and Keiō Teito Electric Railway — separated from Tōkyū, taking over its present lines, and in 1949 its shares were listed on the Tokyo Stock Exchange.

Postwar growth pushed the railway to both the airport and the tip of the Miura Peninsula. The Anamori Line reached the old Haneda Airport station in April 1956 and was renamed the Airport Line on 1 November 1963, the same day the Kurihama Line opened to Nobi; further extensions brought Miurakaigan in 1966 and, on 26 April 1975, Misakiguchi, completing the Kurihama Line. On 21 June 1968 the Sengakuji–Shinagawa section opened and through-running began onto Toei Line 1, today's Toei Asakusa Line. On 1 June 1987 the company renamed ten "Keihin"-prefixed stations to "Keikyū" and unified its abbreviation as Keikyū, partly to distinguish itself from the Keihin-Tōhoku Line of the newly created JR East, and from 21 February 1995 it raised the maximum speed between Shinagawa and Yokohama to 120 km/h.

The modern company is defined by Haneda access and a new Yokohama base. The Airport Line was rebuilt in stages — Anamori-Inari to Haneda (today's Tenkūbashi) opened on 1 April 1993, and on 18 November 1998 trains reached the Haneda Airport terminal station (today's Haneda Airport Terminal 1·2), completing the present operating network: five lines totalling 87.0 km with 73 stations, all standard gauge (1,435 mm) unlike the 1,067-mm gauge more common in Japan. From Sengakuji, Keikyu trains run through onto the Toei Asakusa Line and beyond onto Keisei Electric Railway lines toward Narita Airport and Hokusō Railway lines toward the Chiba New Town area. The bus business was spun off to Keihin Kyūkō Bus on 1 October 2003; the PASMO IC card was introduced on 18 March 2007; and on 21 October 2010 the English corporate name was changed from Keihin Electric Express Railway Co., Ltd. to Keikyu Corporation, with station numbering introduced the same day. On 17 September 2019 the head office moved from Takanawa in Minato, Tokyo, to the newly completed Keikyu Group Headquarters in the Minato Mirai 21 district of Yokohama, consolidating eleven group companies, and the Keikyu Museum opened on its ground floor in January 2020. On 26 November 2022 the company carried out its first large-scale timetable revision in 23 years.

• 189825 February: Daishi Electric Railway Co., Ltd., the founding company of today's Keikyu, was established, with Tachikawa Yūjirō as representative senior managing director.
• 189921 January: the 2.0-km line from Kawasaki (later Rokugōbashi) to Daishi (today's Kawasaki Daishi) opened in standard gauge — the third electric railway company in Japan and the first in the Kantō region. On 25 April the company was renamed Keihin Electric Railway.
• 19301 April: the Shōnan Electric Railway opened its standard-gauge lines from Kōganechō to Uraga and from Kanazawa-Hakkei to Shōnan Zushi, the southern half of today's main-line network.
• 19331 April: Takanawa station was closed and trains were brought into Shinagawa Station; the entire line was regauged back to 1,435-mm standard gauge, and through service between Shinagawa and Uraga began.
• 19411 November: Keihin Electric Railway merged the Shōnan Electric Railway (together with Shōnan Hantō Jidōsha).
• 19421 May: under wartime consolidation, Keihin was merged together with Odakyū into Tōkyō Yokohama Electric Railway, creating Tokyo Kyūkō Electric Railway, the "Dai-Tōkyū" combine.
• 19481 June: Keihin Kyūkō Dentetsu (Keihin Electric Express Railway, today's Keikyu Corporation) was established as a "third company" of Tōkyū and took over the present lines, separating from Tōkyū alongside Odakyū Electric Railway and Keiō Teito Electric Railway.
• 196821 June: the Main Line section from Sengakuji to Shinagawa opened, and through-running began onto Toei Line 1, today's Toei Asakusa Line.
• 197526 April: the Kurihama Line was extended from Miurakaigan to Misakiguchi, completing the line.
• 19871 June: ten stations prefixed "Keihin" were renamed "Keikyū" and the company unified its abbreviation as Keikyū, partly to distinguish itself from the Keihin-Tōhoku Line of the newly created JR East.
• 199818 November: the Airport Line was extended from Tenkūbashi to the Haneda Airport terminal station (today's Haneda Airport Terminal 1·2), completing the present operating network.
• 201021 October: the English corporate name was changed from Keihin Electric Express Railway Co., Ltd. to Keikyu Corporation, and station numbering was introduced at all stations except Sengakuji.
• 20195 September: a limited express train struck a truck near Kanagawa-Shinmachi Station; the truck driver was killed and 33 people were injured.
• 201917 September: the head office moved from Takanawa in Minato, Tokyo, to the newly completed Keikyu Group Headquarters in the Minato Mirai 21 district of Nishi-ku, Yokohama, consolidating the head-office functions of eleven group companies.