growing Chinese cities and often acquired great social and even political influence. Rich merchants with official connections built up huge fortunes and patronized literature, theater and the arts. Cloth and handicraft production boomed. Copper was obtained from Japan. Copper also came from Yunnan. Qing International trade Qing trade policy was broadly isolationist, with the Qianlong Emperor notably proclaiming that Our land is so wealthy and prosperous that we possess all things. Therefore, there is no need to exchange the produce of foreign barbarians for our own. Owing to Ming loyalists like Koxinga, the regent Prince Rui resumed the ban on private foreign trade in 1647. In fact, like the Ming before it, the Qing Empire was dependent on foreign trade for the Japanese and South American silver that underpinned its monetary system, and the ban was not effective until a more severe order followed in 1661 upon the ascension of the Kangxi Emperor. Chinese in Guangdong, Fujian, Zhejiang, Jiangsu, and parts of Shandong were forcibly removed from the coast over the next three years in the Great Clearance. Ships were destroyed, and foreign trade was again limited to that passing through Macao. Following high-level memorials to the throne, the evacuation was no longer enforced after 1669 and, following the destruction of Tungning on Taiwan, the other bans were lifted in 1684. The year after that, customs offices were established in Guangzhou, Xiamen, Ningbo, and Songjiang to deal with foreign trade. The enormous emigration that attended this policy – along with rumors of a Ming pretender in the Philippines – caused the Kangxi Emperor to ban trade in the South China Sea and order the émigrées return upon penalty of death in 1717; this was rescinded ten years later, but the attendant port inspections and restrictions continued. The East India Company's discovery that the prices and duties at Ningbo were both much lower than those at Guangzhou prompted them to begin shifting their trade north in 1755. Following the Qianlong Emperor's failed attempt to discourage this through higher fees, he declared in the winter of 1757 that – effective the next year – a single ghetto southwest of Guangzhou (then romanized as "Canton") was to be the only Chinese port permitted to Western traders, beginning the Canton System. Under this system, a guild of approved and bonded Chinese merchants monopolized China's foreign export trade in exchange for ensuring their foreign partners'