The story
20 August 1899 - Gyeongin Railway from Incheon to Noryangjin (Seoul) opened;
1 October 1902 - Gyeongbu Railway from Yeongdeungpo (Seoul) to Myeonghak (Anyang) opened;
1 November 1903 - Gyeongbu Railway acquired the Gyeongin Railway;
21 February 1904 - Temporary Military Railway established by the Imperial Japanese Army;
28 April 1905 - Military Railway's Gyeongui Line from Yongsan to Sinuiju opened;
1 July 1906 - Railway Office of the Administration of the Japanese Resident-General of Korea established; Gyeongbu Railway nationalised;
1 September 1906 - Temporary Military Railway transferred to the Railway Office and merged with the Gyeongbu Railway to create the National Railway Administration (統監府鐵道管理局, Tōkanfu Tetsudō Kanrikyoku; 통감부 철도관리국, Tonggambu Cheoldogwalliguk);
16 December 1909 - National Railway Administration renamed Korea Railway Administration (鐵道員韓國鐵道管理局, Tetsudōin Kankoku Tetsudō Kanrikyoku; 철도원 한국철도관리국, Cheoldowon Hanguk Cheoldogwalliguk);
Read the full text
29 August 1910 - Korea annexed by Japan, Government-General of Korea established;
1 October 1910 - Korea Railway Administration becomes the Railway Bureau of the Government-General of Korea, (朝鮮總督府鐵道局, Chōsen Sōtokufu Tetsudōkyoku; 조선총독부 철도국, Joseon Chongdokbu Cheoldoguk) (Sentetsu), its operating arm called "Chosen Government Railway" in English;
1 November 1911 - Bridge across the Yalu River completed, establishing a connection to the South Manchuria Railway (Mantetsu);
31 July 1917 - Management of Sentetsu and private railways in Korea transferred to the South Manchuria Railway, Railway Bureau becomes Mantetsu Keijō/Gyeongseong Administration (満鐵京城管理局, Mantetsu Keijō Kanrikyoku; 만철 경성 관리국, Mancheol Gyeongseong Gwalliguk);
1 April 1925 - Management and operation of railways in Korea returned to the Railway Bureau, Sentetsu independent again;
1 October 1934 - Management of the Sentetsu lines north of Cheongjin transferred to the South Manchuria Railway;
12 March 1943 - Railway Bureau abolished, Chosen Government Railway transferred to the Ministry of Transportation.
15 August 1945 - Sentetsu abolished.
After the end of the World War II, all railways in Korea were nationalised, with the lines in South Korea becoming part of the Korean National Railroad, and those in North Korea becoming part of the Korean State Railway.
From Wikipedia’s article on Chōsen Government Railway, shared under CC BY-SA 4.0.4