Meitetsu Gamagōri Line

The line was not built by Meitetsu but by the Mikawa Railway (Mikawa Tetsudō), a private company that was extending its network southward toward the Mikawa Bay coast. On 11 August 1929 the Mikawa Railway opened the section from Mikawa-Yoshida Station (today's Kira-Yoshida) to Mikawa-Toba Station, electrified from the outset at 1,500 V DC. The company then pushed on toward Gamagōri, but lacked the funds to electrify the final stretch, so the remaining Mikawa-Toba–Gamagōri section was extended as a non-electrified line.

The route was completed on 10 November 1936, when the segment from Mikawa-Kashima to Gamagōri opened and through running to Gamagōri began. In its early decades the line enjoyed a heyday as a tourist route, ranked alongside Meitetsu's Inuyama and Chita New lines, and was served by numerous limited expresses running through from the main line to bring sightseers to the Mikawa Bay coast.

In 1941 the Mikawa Railway was absorbed into Meitetsu: on 1 June that year the Nagoya Railroad merged the Mikawa Railway, and the Gamagōri route became part of the larger Meitetsu network. A series of voltage changes followed. On 1 February 1943 the Mikawa-Yoshida–Mikawa-Toba section was reduced from 1,500 V to 600 V so that it could run through with the likewise 600 V Nishio Line. The eastern half of the route was then electrified at 600 V in two steps after the war — Mikawa-Toba to Higashi-Hazu on 31 October 1946, and Higashi-Hazu to Gamagōri on 23 April 1947 — so that the whole line was at last electrified.

The line acquired its own identity on 16 May 1948, when, in a timetable revision, the Mikawa-Yoshida–Gamagōri section was separated from the Mikawa Line and designated the "Gamagōri Line." On 12 July 1959 the line's overhead voltage was raised to 1,500 V, restoring through operation with the Mikawa Line and bringing the whole route to the standard 1,500 V DC it still uses.

As leisure habits changed and tourism to Mikawa Bay declined, the line lost its excursion traffic and was gradually reduced to a commuter role. One-person (driver-only) operation began across the whole line on 1 June 1998. A timetable revision on 29 June 2008 ended the remaining through trains to the Nishio Line, after which the Gamagōri Line carried only one-person local trains shuttling back and forth within the line itself. When Meitetsu introduced its "manaca" IC fare card on 11 February 2011, the card was not rolled out on the Mikawa-Toba–Gamagōri section, leaving part of the line outside the IC ticketing system.

With ridership low, the line became financially precarious and was identified as a candidate for possible discontinuation. From fiscal 2010 the cities of Nishio and Gamagōri together provided about 250 million yen a year in operating support — split roughly 150.69 million yen from Nishio and 99.31 million yen from Gamagōri — while Aichi Prefecture added a combined 83 million yen a year to the two cities. Even so the line ran deeply in the red: in fiscal 2017 the Nishio–Gamagōri section earned about 390 million yen against expenditure of about 1.16 billion yen, a loss of roughly 770 million yen. Under continued subsidy agreements the line has remained in service, and a new framework has been arranged under which Nishio and Gamagōri are to support Meitetsu with on the order of 400 to 450 million yen a year from fiscal 2027.

• 192911 August: the Mikawa Railway opens the Mikawa-Yoshida (now Kira-Yoshida)–Mikawa-Toba section, electrified at 1,500 V DC.
• 193610 November: the Mikawa-Kashima–Gamagōri section opens, completing the route through to Gamagōri; the Mikawa-Toba–Gamagōri portion opens non-electrified for lack of funds.
• 19411 June: the Nagoya Railroad (Meitetsu) merges the Mikawa Railway; the line becomes part of the Meitetsu network.
• 19431 February: the Mikawa-Yoshida–Mikawa-Toba section is reduced from 1,500 V to 600 V to allow through running with the 600 V Nishio Line.
• 194631 October: the Mikawa-Toba–Higashi-Hazu section is electrified at 600 V.
• 194723 April: the Higashi-Hazu–Gamagōri section is electrified at 600 V, completing electrification of the whole route.
• 194816 May: in a timetable revision, the Mikawa-Yoshida–Gamagōri section is separated from the Mikawa Line and designated the 'Gamagōri Line'.
• 195912 July: the line's overhead voltage is raised to 1,500 V, restoring through operation with the Mikawa Line.
• 19981 June: one-person (driver-only) operation begins across the whole line.
• 200829 June: a timetable revision ends the remaining through trains to the Nishio Line; the line is left with only in-line one-person local trains.
• 2010From fiscal 2010, Nishio and Gamagōri together provide about 250 million yen a year in operating support (about 150.69 million from Nishio, 99.31 million from Gamagōri), with Aichi Prefecture adding 83 million yen a year.
• 201111 February: the 'manaca' IC card is introduced on Meitetsu, but is not rolled out on the Mikawa-Toba–Gamagōri section.
• 2017In fiscal 2017 the Nishio–Gamagōri section earns about 390 million yen against about 1.16 billion yen in expenditure — a loss of roughly 770 million yen.
• 2027Under a new framework, Nishio and Gamagōri are to support Meitetsu with on the order of 400 to 450 million yen a year from fiscal 2027.