一口通商
The Old China Trade () refers to the early commerce between the Qing Empire and the United States under the Canton System, spanning from shortly after the end of the American Revolutionary War in 1783 to the Treaty of Wanghia in 1844. The Old China Trade represented the beginning of relations between the United States and East Asia, including eventually U.S.–China relations. The maritime fur trade was a major aspect of the Old China Trade, as was illegal trafficking in opium, with the trade era overlapping the First Opium War waged by China against Western traders and blockade-runners between 1839-1842.