The Chosen Government Railway nationalised the privately ownedTomun Railway on 1 April 1929, acquiring the private railway's route from Hoeryŏng to Tonggwanjin and calling it the "West Tomun Line". Intending to create as short a route as possible from Japan to Manchuria, Sentetsu had started building its own "East Tomun Line" from Unggi towards Tonggwanjin in 1929, eventually reaching Namyang on 1 December 1932, and finally closed the final gap between Namyang and Tonggwanjin on 1 August 1933, thus completing the Tomun Line from Hoeryŏng to Unggi; Tonggwanjin station was renamed Tonggwan at that time. At the same time as the Namyang–Tonggwan section of the mainline was opened, a bridge was built over the Tumen River at Namyang, along with a line to Tumen, Manchukuo. This connected Sentetsu to the Manchukuo National Railway's new Jingtu Line from Xinjing, capital of Manchukuo, to Tumen, that was also opened in 1933. This established the desired shortest-possible connection from Japan to Harbin via the Korean ports of Ch'ŏngjin and Unggi through Xinjing. On 1 October 1933, management of Sentetsu's entire route from Ch'ŏngjin to Unggi was transferred to the South Manchuria Railway, and on 1 November 1934 the Unggi–Namyang section of the Domun Line and the Namyang–Tumen line were merged to form Mantetsu's North Chosen East Line ; the Namyang–Sambong section became the North Chosen West Line. In 1936, the "Asahi" express train between Xinjing and Rajin was inaugurated, to connect to the ferry from Rajin to Japan. In 1940, management of the Ch'ŏngjin–Sambong route was transferred back to Sentetsu, which made it part of its Hamgyeong Line; Mantetsu continued to manage the North Chosen East Line, eventually acquiring outright ownership of the line.
Services
The line is used for import-export traffic between the DPRK and China; the primary exports shipped through to China are magnetite, talc and steel, and the main import is coke. These trains are often hauled by Chinese or Korean DF5-type locomotives.
Route
A yellow background in the "Distance" box indicates that section of the line is not electrified.