後三国時代
In the Later Three Kingdoms era, the Ansan area was owned by Taebong (also known as Hugoguryeo, "Later Goguryeo") in Silla Hyogong's 4th year (AD 900). After then, Gung Ye, who was ruler of Taebong, was overthrown by Wang Geon, and the Ansan area was turned over to Goryeo, founded by Wang Geon. First the Gung Ye Ganggu-gun was changed to Ansan-gun but the state of the military was preserved.