Gimpo first began as a Japanese military airfield built in 1939 on flat land west of Seoul. American forces later used the same field during and after the Korean War. It became Seoul's main international airport in 1958, replacing an older field called Yeouido. Grew into one of Asia's major gateways as South Korea's economy grew fast. New passenger terminals opened in the late 1970s and 1980s.
The airport handled the huge traffic surge of the 1988 Seoul Olympics, which brought thousands of visitors from all over the world into the capital. Everything changed suddenly on 29 March 2001, when Incheon International Airport opened on reclaimed land off the coast and took over almost all of the international flights. Gimpo turned into a domestic only airport in a single night.
It did not stay that way for long. From 2003, short international routes slowly returned under deals struck between countries, first to Tokyo Haneda, then to Shanghai, Osaka, Beijing, and Taipei. All were city center airports paired with Gimpo on purpose. Today it is South Korea's second busiest airport overall, driven by the Jeju route, which is often the busiest airline route in the world by seats offered on planes.