918 -- Wang Geon establishes the Goryeo Kingdom, unifying three states on the Korean Peninsula. One of them, the Silla Kingdom, had declined following its 1,000-year rule that started in 57 B.C. The other two states -- post-Baekje and post-Koguryo -- had briefly emerged in the southwestern and the northern parts of the peninsula with historic legacies tied to the Baekje and Koguryo kingdoms.