Uno Line

The entire line opened in one step on 12 June 1910, built by the state railways to reach the harbour at Uno on the Inland Sea. On the same day, the Uko ferry connection across the strait began operating, linking Uno with Takamatsu on the island of Shikoku. For most of the twentieth century the Uno Line existed chiefly to feed this ferry: it was the principal rail-and-sea route between Honshū and Shikoku, and Uno was its Honshū gateway. The line was first measured in imperial units — the opening distance of 20.4 miles was converted to a metric figure of about 32.9 km in 1930.

The stations along the line were reshaped repeatedly in the early decades. Several original stops were renamed — Shikano became Ōmoto in 1925 when the Okayama–Senoo routing was altered and the station moved, Ajino became Hikosaki in 1914, and Yuga became Sakogawa in 1952. A cluster of five new stations opened on 1 January 1939, were suspended in November 1940 during wartime retrenchment, and were brought back into service on 15 November 1950. Kuguhara Station was added in 1952.

The line was modernised in the post-war decades. After fifty-anniversary ceremonies in June 1960 and a farewell run for its diesel cars that September, the whole line was electrified on 1 October 1960 and electric-train operation began. Automatic block signalling followed in 1961, the ATS-S safety system was fitted line-wide in 1963, and centralised traffic control was introduced in 1970. When the Sanyō Shinkansen was extended to Okayama in March 1972, the daytime limited and express trains that had used the line were withdrawn and rapid-service trains began running instead.

With the privatisation and break-up of Japanese National Railways on 1 April 1987, the Uno Line was inherited by JR West, while Japan Freight Railway became a Class II operator over the whole line. That same spring, on 28 March 1987, a rapid service named the "Bisan Liner" began running using new 213 series electric cars. The arrangement was short-lived, because the great fixed link to Shikoku was about to open.

The decisive change came on 10 April 1988, when the Seto-Ōhashi (Great Seto Bridge) opened and the connecting Honshi-Bisan Line entered service, at last carrying trains directly from Honshū to Shikoku by rail. The new "Marine Liner" rapid service began running across the bridge, and on the previous day the "Bisan Liner" rapid, the long-serving Uko ferry, and its hovercraft service were all discontinued; only a JR high-speed boat on the Uko route survived for a time, itself suspended in 1990 and abolished the following year. The Uno Line's century-old role as the gateway to the Shikoku ferry thereby came to an end. The Okayama–Chayamachi section was absorbed into the role of approach line for the bridge route and remains heavily used, while the Chayamachi–Uno section became a more local route serving Tamano.

In the decades since, the line has been steadily upgraded. The area around Ōmoto Station was elevated by late 2001, one-man operation began on the Chayamachi–Uno section in 2001, and a roughly 3.3-kilometre stretch between Bitchū-Mishima and Chayamachi was double-tracked by early 2009, with a revised timetable reflecting the new capacity from March 2009. ICOCA smart-card acceptance reached the Okayama–Chayamachi section in 2007 and was extended to the rest of the line in 2019, giving full coverage. From 26 March 2016 the line gained a line colour, a route symbol and its "Uno Minato Line" nickname; station numbering was rolled out from 2020. One-man operation was introduced on local trains between Okayama and Chayamachi in March 2025.

• 191012 June: the entire Uno Line opens between Okayama and Uno (20.4 miles, ≈32.83 km), built to reach Uno port; the Uko ferry to Takamatsu begins operating the same day.
• 19141 July: Ajino Station is renamed Hikosaki.
• 19256 March: the Okayama–Senoo routing is altered; Shikano Station is relocated and renamed Ōmoto.
• 19301 April: the line's distance notation is converted from miles to metres (20.4 mi → 32.9 km).
• 19391 January: five new stations open (Bizen-Nishiichi, Bitchū-Mishima, Bizen-Kataoka, Tsuneyama, Bizen-Tai); they are suspended on 1 November 1940 during wartime retrenchment and resume service on 15 November 1950.
• 1952Kuguhara Station opens (20 March); Yuga Station is renamed Sakogawa (15 November).
• 19601 October: the whole line is electrified and electric-train operation begins, following 50th-anniversary ceremonies in June and a diesel farewell run on 30 September.
• 19631 September: the ATS-S safety system is fitted line-wide (automatic block signalling having been introduced in 1961).
• 19705 April: centralised traffic control (CTC) is introduced.
• 197215 March: with the Sanyō Shinkansen extended to Okayama, daytime limited/express trains are withdrawn and rapid services begin.
• 19871 April: JNR is privatised; JR West inherits the line and Japan Freight Railway becomes a Class II operator over the whole line. On 28 March a rapid service ('Bisan Liner') had begun using new 213 series cars.
• 198810 April: the Seto-Ōhashi (Great Seto Bridge) opens and the Honshi-Bisan Line enters service; the 'Marine Liner' rapid begins. The day before, the 'Bisan Liner' rapid, the Uko ferry and its hovercraft are all discontinued, ending the line's role as the gateway to the Shikoku ferry.
• 200925 January: about 3.3 km between Bitchū-Mishima and Chayamachi is double-tracked; a revised timetable reflecting the new capacity takes effect on 14 March.
• 201626 March: a line colour, route symbol and the nickname 'Uno Minato Line' (Uno Port Line) come into use across the line.
• 201916 March: ICOCA acceptance is extended to the Chayamachi–Uno section, giving the whole line smart-card coverage (Okayama–Chayamachi having been added in 2007).
• 202515 March: one-man operation begins on local trains between Okayama and Chayamachi.