What US industry employed over 3,000 African Americans (1/6 of labor force) from 1803-1860?

The account of the Hearings before the United States Commission on CIVIL RIGHTS Vol. 1 - Voting, held in February 16-20,1965 in Jackson Mississippi

“Employment of Laborers of African Extraction in the Island of St. Croix”, 37th Congress. June 6, 1862

Hon. John P. Hale (NH) "The Wrongs of Kansas", given Feb. 26, 1856