History of Seoul Settlement began in Baekje , Wirye-seong , in 17 BC . . It became the capital of the Joseon Dynasty in 1394. There were some modernization efforts by the late 19th century and Seoul became the first city in East Asia to have electricity, trolley cars, water, telephone, and telegraph systems all at the same time . During the Japanese colonial period in the early 20th century, the city was called Gyeongseong . In 1950, during the Korean War, Seoul was occupied by North Korean troops and the city was almost entirely destroyed. The city was retaken by UN Forces on 14 March 1951.