The history of Gimpo dates back to the era of the Three Kingdoms of Korea, and for centuries it has played an important role in South Korea's history due to its strategic location. Its name, which translates as "golden port" or "golden harbor," hints at its historical significance in trade and logistics. The first documented mention of the area dates back to 475 AD, when it was known as Kompho and was part of the ancient state of Goguryeo. Later, after the Silla state unified most of the Korean Peninsula, a district with the modern name of Gimpo was formed here in the 8th century.
Geography played a key role in the city's formation. Its location at the mouth of the Han River, near the capital, made Gimpo an important defensive and transport hub. Proximity to the Yellow Sea fostered maritime communications, defining the city's dual function as both a trading port and a military outpost. A striking example of its defensive importance is Munsu-sanseong Fortress, built in 1694 to protect the approaches to Ganghwado Island and the capital.
During the Joseon Dynasty, Gimpo's administrative status changed several times: it was temporarily part of neighboring lands but was later restored as an independent unit. In 1632, its status was elevated to a county (gun), which strengthened its position in the region. The economy of early Gimpo was closely tied to its role as the "gateway" to the capital. Goods passed through its harbor, and the surrounding fertile lands were an important agricultural area supplying the capital region.