Voyage of the Empress of China, 1784. See this site for a detailed history of early US-China trade.

A passage in Chapter 1 of Moby Dick describes a vigorous trade with the far East: “Posted like silent sentinels all around the town, stand thousands upon thousands of mortal men fixed in ocean reveries … some looking over the bulwarks of ships from China.”

However, trade between China and the U.S. commenced in 1784, just after the Treaty of Paris was ratified; by 1799, when Benito Cereno is set, it would still have been a relatively young trading relationship, especially considering the lengthy sea voyages required.

Principal commodities exchanged included the items mentioned by Capt. Delano (silks, sealskins, coin (specie), as well as ginseng tea, porcelain "China ware," lead, and cotton goods.<br> A.D. Edwards, Empress of China at Mart's Jetty, Port Pirie, 1876

-- Robert Bennet Forbes, Remarks on China and the China Trade. Samuel N. Dickinson, printer, 1844.