Gyeongui Line (1904–1945)
Following Japan's defeat in the Pacific War and the subsequent partition of Korea, the Gyeongui Line was divided at the 38th parallel between North and South Korea. On 25 August 1945, the Soviet Army began operating trains on the line north of Sariwon, whilst trains in the south terminated at Gaeseong. In 1946, the railways in both North and South were nationalised, creating the Korean National Railroad in the South and the Korean State Railway in the North. After the Korean War, the Gyeongui Line was split into three sections. In the South, the Seoul–Jangdan section became the KNR's Gyeongui Line, retaining the same name; in the North, the Bongdong–Pyeongyang section became the P'yŏngbu Line, whilst the Pyeongyang–Sinuiju section became the P'yŏngŭi Line.
Hwanghae Province
In 1953, at the end of the Korean War, the Northern Limit Line was established, which marked the maritime boundary between North and South Korea. The line runs between the mainland portion of Gyeonggi Province that had been part of Hwanghae before 1945, and the adjacent offshore islands (the largest of which is Baengnyeongdo). As a result, the mainland portion reverted to North Korean control, while the islands remained a part of South Korea. (Since 1999, North Korea has claimed a more southerly Maritime Military Demarcation Line, which would make the islands a part of North Korea as well. Disputes between North and South Korean naval vessels often occur in this area.)