They were notably influenced by songs of African Americans, such as those sung whilst manually loading vessels with cotton in ports of the southern United States. The work contexts in which African-Americans sang songs comparable to shanties included: boat-rowing on rivers of the south-eastern U.S. and Caribbean; the work of stokers or "firemen", who cast wood into the furnaces of steamboats plying great American rivers;and stevedoring on the U.S. eastern seaboard, the Gulf Coast, and the Caribbean—including "cotton-screwing": the loading of ships with cotton in ports of the American South. During the first half of the 19th century, some of the songs African Americans sang also began to appear in use for shipboard tasks, i.e. as shanties.