Tsurumi Line

The Tsurumi Line did not begin as a state railway but as a private freight operation. In 1924 the Tsurumi Rinkō Railway (鶴見臨港鉄道, "Tsurumi Port Railway") was incorporated under the leadership of the Asano zaibatsu, with the industrialist Asano Sōichirō as its president, to move goods across the land that the Asano interests and their partners were reclaiming from Tokyo Bay for factory use.

The railway opened on 10 March 1926 as a goods line, running from Hama-Kawasaki to Bentenbashi together with the branch toward Ōkawa, linking the new wharves and works to the national network. In 1928 the main line was pushed on to Ōgimachi, extending the freight artery deeper into the reclaimed industrial zone.

Passenger service came at the start of the 1930s. In 1930 the company electrified its lines at 600 V DC and opened the Tsurumi–Bentenbashi section, and regular passenger trains began running, turning the freight railway into a workers' commuter line as well. The Umi-Shibaura branch then took shape in two stages: the Asano–Shin-Shibaura section opened as a freight-only line in 1932, and in 1940 it was extended to Umi-Shibaura, with passenger service beginning when the extension opened — the platform at the terminus famously sitting on the very edge of the water inside Toshiba's premises.

The Second World War brought the private line into state hands. On 1 July 1943 the Tsurumi Rinkō Railway was designated a wartime-purchase private railway (戦時買収私鉄) and nationalised, becoming the Tsurumi Line of the national railways. The line's industrial setting and its dense web of factory sidings made it exactly the kind of strategic freight feeder the wartime government brought under direct control.

Under national operation the line was modernised incrementally. In 1948 the overhead voltage was raised from 600 V to 1,500 V DC, bringing it into line with the surrounding network. Traffic peaked in the post-war industrial boom: in 1961 the line carried about 37.66 million passengers, its highest annual figure on record. As ridership later eased and operating practice changed, every station except Tsurumi was made unstaffed in 1971, a condition the small wayside platforms retain to this day.

When Japanese National Railways was broken up and privatised on 1 April 1987, the Tsurumi Line passed to the newly created East Japan Railway Company (JR East), which has run it ever since. Although it remained a JR East line, much of its character — short trains shuttling factory workers across a maze of industrial spurs — carried over essentially unchanged from the Tsurumi Rinkō era.

The line's rolling stock was renewed only recently. New-build trains had not been delivered to the Tsurumi Line since the Tsurumi Rinkō Railway's own days, so the introduction of the E131 series, which entered service on 24 December 2023, marked the first new cars in roughly eighty years. By 16 March 2024 all eight E131 sets were in service and the previous 205 series ended regular operation, completing the changeover on a line that even now keeps its original purpose as a lifeline for the Keihin factory district.

• 1924The Tsurumi Rinkō Railway (Tsurumi Port Railway) is incorporated under the leadership of the Asano zaibatsu, with Asano Sōichirō as president.
• 192610 March: the Tsurumi Rinkō Railway opens the Hama-Kawasaki–Bentenbashi line and the Ōkawa branch as a freight line.
• 192818 August: the main line is extended from Hama-Kawasaki to Ōgimachi.
• 193028 October: the lines are fully electrified (at 600 V DC), the Tsurumi–Bentenbashi section opens, and passenger services begin.
• 193210 June: the Asano–Shin-Shibaura section (the future Umi-Shibaura branch) opens as a freight-only line.
• 19401 November: the branch is extended from Shin-Shibaura to Umi-Shibaura as a passenger line.
• 19431 July: the Tsurumi Rinkō Railway is designated a wartime-purchase private railway and nationalised, becoming the Tsurumi Line.
• 19481 May: the overhead voltage is raised from 600 V to 1,500 V DC.
• 1961Annual ridership reaches about 37.66 million passengers, the line's highest figure on record.
• 19711 March: every station except Tsurumi is made unstaffed.
• 19871 April: with the breakup and privatisation of Japanese National Railways, the line is inherited by the East Japan Railway Company (JR East).
• 201620 August: station numbering is introduced, with Tsurumi Line stations assigned numbers JI01–JI10.
• 202324 December: the E131 series enters service — the first new-build trains on the line since the Tsurumi Rinkō Railway era, roughly eighty years earlier.
• 202416 March: all eight E131 sets are in service and the 205 series ends regular operation.