The line is composed of sections opened by four different railway companies, which were then nationalised and linked by the JGR/JNR.
DMU train on Kisei main line in 1979
In 1891, the Kansai Railway opened the Kameyama to Tsu section, with the Sangu Railway opening the Tsu to Shoka section in 1893. At the western end, the Kiwa Railway opened the Wakayamashi to Wakayama section in 1903, and was acquired by the Kansai Railway the following year. The Kansai Railway and the Sangu Railway were nationalised in 1907. In 1912, the Shingu Railway opened the Kii-Katsuura to Miwasaki section, extending the line to Shingu the following year. The company was nationalised in 1934. On the eastern side of the Kii Peninsula, the Japanese Government Railway (JGR) extended the line from Shoka to Owase in sections between 1923 and 1934, whilst on the western side, it extended the line from Wakayama to Esumi in sections between 1924 and 1938. In 1935, the Kii-Katsuura to Taiji section was opened by JGR, extended to Kushimoto the following year, and to Esumi in 1940, providing a link to Wakayama and Osaka. The successor to JGR, the Japanese National Railways (JNR), opened the Owase to Shingu section in stages between 1956 and 1959, completing the line.
Double-tracking
The Akogi to Takajaya section was double-tracked in 1909, with the Matsusaka to Tokuwa section double-tracked two years later. In 1944, both sections were returned to single track and the recovered materials recycled for the Japanese war effort. The Wakayama to Kii-Tanabe section was double-tracked in stages between 1964 and 1978.
Electrification
The line was electrified between Wakayama and Shingu in 1978, with the Wakayama to Wakayamashi section being commissioned in 1984.
Other notable dates
CTC signalling was commissioned between Wakayama and Shingu in 1978, and extended to Kameyama in 1983.
Freight services ceased in 1986.
Former connecting lines
Arita Railway train, 2002Nogami Electric Railway at Kainan
Akogi Station: The Chusei Railway operated a 6 km 762 mm (2 ft 6 in) gauge line between Iwatahashi and Hisai between 1909 and 1942. At Hisai, it connected to the Dainippon Railway 15 km 762 mm gauge line to Ise-Kawaguchi on the Meisho Line between 1925 and 1942.
Matsusaka Station: Mie Kotsu operated 20 km 762 mm line to Oishi between 1912 and 1964. The line was electrified at 600 V DC in 1927, although steam locomotives continued to be used until 1938.
Tokuwa Station: The Ise Electric Railway "main line" connected here between 1930 and 1941.
Funatsu Station: The Osugidani forest railway connected here to haul cedar. It was opened between 1929 and 1952 utilising 762 mm gauge, and featured a 17 km "main line" and nine branches of between 1 km and 11 km in length, as well as two cable-hauled inclines. The last line closed in 1974.
Fujinami Station: The 9 km Arita Railway line between Yuasa and Kanaya which operated between 1915 and 2003 connected at this station.
Kainan Station: The Nogami Electric Railway operated an 11 km line, electrified at 600 V DC, to Noburu-Yamaguchi between 1916 and 1994. Freight services operated between 1951 and 1971.
Wakayama station - A 3 km line to Higashi-Matsue on the Nankai Kada Line opened in 1912. The line was electrified at 600 VDC in 1930, and closed in 1955.
Kiwa Station: The Kishigawa Line commenced from this station from 1917 until the terminus was truncated 3 km to Wakayama in 1924.
^ ab紀勢本線・参宮線でキハ11形からキハ25形へ置換え [Switch from KiHa 11 to KiHa 25 on Kisei Main Line and Sangu Line]. Japan Railfan Magazine Online (in Japanese). Japan: Koyusha Co., Ltd. 3 August 2015. Retrieved 3 August 2015.
