The Mikawa Railway opened the Ōhama-minato to Kariya-shin section in 1914, and extended the line to Chiryū the following year, to Koromo in 1920 and Sanage in 1924. In 1926, the Sanage to Hekinan section was electrified at 1,500 V DC, and in the same year the Hekinan to Matsukijima section opened as an electrified section, as were all subsequent extensions. The Sanage to Nishi Nakagane section opened between 1927 and 1928, and the Matsukijima - Mikawa Yoshida section also opened in the latter year. The company merged with Nagoya Railroad in June 1941, and the Mikawa Yoshida - Kira Yoshida section opened in 1943, connecting to the Gamagōri Line and the Nishio Line. Construction of an ~ extension from Nishi Nakagane to Asuke had commenced in the 1930s, with the roadbed completed when the Pacific War commenced. Shortage of materials resulted in the rail line never being laid, and the proposed extension was formally abandoned in 1958, with the roadbed being converted to a public road, which is readily identifiable on aerial photographs. Freight services ceased in 1984, and as a result of declining patronage, the electrification on the Sanage - Nishi Nakagane section was decommissioned in 1985, and on the Hekinan to Kira Yoshida section in 1990, DMUs then providing the passenger service. Patronage continued to decline, and both sections were closed in 2004.
Double-tracking
The Chiryū to Shigehara section was double-tracked in 1976, the Kariya to Kariyashi section in 1980, and the Umetsubo to Toyotashi section in 1986. The doubling of the Toyotashi to Chiryū section is proposed, and some works have been undertaken, but funding issues with the local governments has stalled further work at present. The land has been acquired to double the Shigehara to Kariya section, but Meitetsu does not consider the patronage levels on this section justify duplication at this stage.
Former connecting lines
Uwa Goromo Station: The Okazaki Electric Railway opened a line, electrified at 600 V DC, from Okazaki-Ida to Modachi in 1924. The line was proposed to continue to Matsudaira, but the company encountered financial difficulties and merged with the Mikawa Railway in 1927, which opened the Uwa Goromo to Mikawa Iwawaki section two years later, and converted the line to 1,500 V DC. In 1939, the Mikawa Iwawaki to Modachi section closed, and in 1941, the company merged with Meitetsu. The Okazaki-Ida to Daijuji section closed in 1962, and as a result of flood damage caused by torrential rain, the balance of the line closed in 1972. At Okazaki-Ida, there was a connection to a tram line that connected to the Tokaido Main Line at Okazaki station, the tramway also closing in 1962.
