Chengdu is one of the 24 well-known historical cities approved by the Sichuan provincial committee and the State Council of China. 2,300 years ago, King Kaiming the 1Xth of the Shu State relocated his capital here. In 256BC, the Shu County Governor Li Bing and his son built the Dujiang Dam. Since then the Chengdu plain has never had any flood or drought disasters and its farm and handicraft industries have prospered. The Chengdu plain has hence been referred to as the "Kingdom of Heaven." Since then, Chengdu has become the state capital of Sichuan, and an important political, economic, cultural and military center in the southwest. It was one of the 5 famous cities in Han Dynasty, and the best commercial city second to Yangzhou only in Tang Dynasty. It was also the second largest cosmopolitan city of the North Song Dynasty (960-1127) next to its capital city Bianjing, where Jiaozi, the earliest paper money in the world, was first circulated.