On October 25, 1927, the Ministry of Railways opened the first section between Rumoi and Ōtodo from the south. Less than a year later, on October 1, 1928, the extension to Onishika is opened. In operational terms, the line was then considered a branch of the Rumoi Main Line, it could only be reached from Rumoi by changing direction at the Higashi-Rumoi siding to the east of the station. After the line reached Kotambetsu Station on August 15, 1931,[2] it was no longer considered a branch of the Rumoi Main Line on October 10 of the same year and was named the Haboro Line.[3] Finally, on September 1, 1932, it extended to the namesake town of Haboro.[2]
Remains of Kotambetsu Station
Around this time, the Ministry of Railways began construction of the Teshio Line (天塩線, Teshio-sen) from the north. The section between Horonobe and Teshio went into operation on June 30, 1935, followed by the Teshio-Embetsu section on October 23, 1936. The Haboro Line was extended from Haboro to Chikubetsu on December 9, 1941, where it connected to a strategically important mine railway. On the same day, it was given a direct route between Rumoi and Santomari, eliminating the inconvenience of reversing via the Higashi-Rumoi siding. Due to the Pacific War and the economic problems in the post-war period, further line construction was suspended for over a decade. On November 6, 1957, the Japanese State Railway, which was now in charge, put the Chikubetsu-Shosambetsu section into operation. Finally, it completed the line on October 18, 1958, with the closing of the gap between Shosambetsu and Embetsu, whereby the previous Teshio Line was merged into the Haboro Line.[2]
In 1962, the Japanese National Railways introduced diesel locomotive for passenger transportation, as well as a daily pair of express trains from Horonobe via Rumoi to Sapporo. The closure of coal mines, the decline in herring fishing and the expansion of the road network caused the volume of traffic to plummet. Freight transport facilities were gradually abandoned and express train services were discontinued on November 1, 1986.[4] Finally, on March 30, 1987, two days before its privatization, JNR closed down the entire length of the Haboro Line. Since then, a bus route has been operated by Engan Bus.[5]
