During the 3rd century, during the Three Kingdoms period, Mahan's Bulsa Bunya Kingdom (不斯濆邪國) was located here. Later, Baekje annexed this area and established Bunchagun (分嵯郡), which was also called Bulsa (弗斯) or Busa (夫沙). In 757, King Gyeongdeok of Unified Silla changed it to Bunryeonggun (分嶺郡). During the Goryeo Dynasty, it was changed to Nakangun.
There is a record that in the 6th year of King Taejo's reign (1397), General Kim Bin-gil built an earthen fortress to prevent the invasion of Japanese pirates, and in the 9th year of King Sejong's reign (1426), it was rebuilt into a stone fortress to reinforce defense.