[1] Construction of a railway line running north from Hanseong had been envisioned since the end of the 19th century, but the lack of funding led to the failure of several attempts.

Imperial Japan, which had gained the concession to build the Gyeongbu Line from Seoul to Busan, recognised that a railway running through all of Korea from north to south would serve as a means to strengthen its influence over Korea, sought to gain control of the Gyeongui Line project as well.

[2] When the Russo-Japanese War broke out in 1904, Japan ignored Korea's declaration of neutrality, transporting troops to Incheon and forcing the Korean government to sign an agreement that gave Japan's military control of railway projects if deemed necessary for military operations.

In the following year, bridges were completed over the Cheongcheon and Daedong rivers, allowing for the operation of through trains between Yongsan and Sinŭiju.

[7] The National Railway initiated passenger service on the Gyeongui Line on 1 April 1908, and Korea's first express train, the "Ryūki", began operating between Sinuiju and Busan via Gyeongseong.

On 13 May 1916, the Mitsui Mining Railway (called Gaecheon Light Railway after 1927) opened the narrow gauge Gaecheon Line from Sinanju to Gaecheon, Sentetsu opened the Bakcheon Line from Maengjungni to Bakcheon on 10 December 1926, on 27 September 1939 the Pyeongbuk Railway opened its line from Jeongju to Cheongsu and Supung, where the Supung Dam was built; the Emperor of Manchukuo, Puyi, visited the Supung Dam, travelling by rail via the Gyeongui Line and the Pyeongbuk Railway.

[7] Passenger service was expanded in the 1930s, seeing the introduction of the "Hikari" limited express running from Busan to Xinjing, Manchukuo, in November 1934; then, in November 1939, the North China Transportation Company, in conjunction with Sentetsu and Mantetsu, introduced the "Koa" and "Tairiku" limited express trains, running between Pusan and Beijing.

By 1943 traffic levels were sufficiently high to justify double tracking of the entire line between P'yŏngyang and Sinŭiju, with the work being completed on 15 May 1943.