Construction of the Ongjin Line proper began from Haeju Station, with the first section to Ch'wiya (nowadays called Pyŏksŏng) opened on 11 December 1936.

In May 1937, two new stretches were opened: a short (0.7 km (0.43 mi)) section from Tongp'o to Chŏngdo on the 10th,[6] and from Ch'wiya to Ongjin on the 19th.

[8] Following the end of the Pacific War, the subsequent partition of Korea left the Ongjin Line divided between the Soviet and American zones of occupation, with the 38th parallel splitting the line near Chayang Station.

Electrification of the East Haeju—Wangsin—West Haeju section of the line was completed by April 1982.

[9] A yellow background in the "Distance" box indicates that section of the line is not electrified.