During the Qing Dynasty, Yunnan Province was rich in copper but poor in salt, while Guangdong Province was the opposite, with abundant salt but insufficient copper. Based on the complementary nature of copper and salt resources in the economic

structure of the two provinces, as well as the urgent and continuous demand for each other's resources, in the 19th year of the Qianlong reign, the Qing court authorized Yunnan and Guangdong to implement the Copper-Salt Exchange. This not only solved the predicament of salt shortage in southeastern Yunnan, stabilized the Yunnan border market, but also guaranteed the normal operation of Guangdong Province minted coins, stabilized the financial market in Guangdong, and alleviated the problem of excess sea salt in Guangdong.Copper and salt were the major commodities in the inter-provincial trade between Yunnan and Guangdong, and the Copper-Salt Exchange played an important role in maintaining and promoting the development of the inter-provincial trade between Yunnan and Guangdong, as well as constructing a regional market spanning Yunnan, Guangxi, and Guangdong, which interacted with each other and was connected as one.