In the post-Revolution era, African slavery was waning as cotton production was a laborious task and not worth cultivating on a large scale until Eli Whitney of Massachusetts revolutionized the industry in 1793. Thereafter, New England mills could not live without raw slave-produced cotton, Manhattan lenders ensured plantation owners that money was available for plantation expansion, and New England slavers continued to import the labor supply.
Bernhard Thuersam, Chairman
North Carolina War Between the States Sesquicentennial Commission
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New York's Notorious Slave Ships
"In the decade 1850-1860 Great Britain maintained consulates in six Southern ports: Norfolk, -- changed to Richmond in 1856 – Charleston, Savannah, Mobile, New Orleans and Galveston.
[Consul G.P.R.] James [in Norfolk and Richmond] . . . considered that Virginians were very kind to their slaves and that slavery was an injury to masters rather than Negroes. One of the proprietors of the Richmond "slave warehouse" was, wrote his son Charles later, an "unmistakable Yankee," said to be very humane to his charges, "but the business was regarded as infamous. I heard a respectable man denounced for accepting his hospitality."
At Niagara Falls, James saw a runaway Negro belonging to one of his Norfolk neighbors; he had found it difficult to make a living and was cold and he begged the consul to ask his owner to take him back.
[Consul] Henry G. Kuper of Baltimore gave assurance that the slave trade was being extensively carried on by many American citizens, especially in New York . . . with the connivance of Spanish authorities in Cuba where most of the cargoes were conveyed . . . Consul Edward W. Mark wrote from Baltimore that at any moment twenty vessels might be found under construction at that port, admirably adapted for the slave trade. Some were built expressly for the trade by "respectable houses," which would not enter the trade themselves but merely executed the orders they received.
Mark believed, however, that in Baltimore little countenance was given to the trade. It was carried on rather "from New York and the eastern parts of the Union . . . and generally by New England and foreign firms."
[In 1858 Consul] Molyneaux of Savannah told the story of a Charleston mercantile house . . . which proposed to send the ship Richard Cobden . . . on a [suspicious] voyage to Africa to bring "free emigrants" to a United States port. The collector of the port appealed to United States Secretary of the Treasury Howell Cobb who pronounced the proposal illegal.
About the same time the Lydia Gibbs, a vessel of one-hundred and fourteen tons of Northern build, sailed from Charleston under one Watson, a Scotchman naturalized in the United States. He took it to Havana where it was sold to unknown persons for $12,000. Watson was to receive $6,000 more if he escaped detection, and in addition a certain percentage of the slaves he should succeed in landing in Cuba.
[In July 1858 Charleston Consul Robert Bunch] wrote that the brig Frances Ellen had cleared from Charleston for Africa, supposedly to engage in the slave trade; that the firm of Ponjand and Lalas, two Spaniards, which sent it out, was believed to be regularly engaged in this traffic [and] intended to land five or six cargoes in Texas . . .
In December, 1859, the South Carolina legislature received from the New York assembly a set of resolutions passed by the latter body, condemning the slave trade and urging the Southern States not to connive at or encourage the odious traffic. South Carolina returned the resolutions to the senders without comment and Bunch, though agreeing with the New York sentiments, dryly noted that the action was not "happily received," "as it is notorious that, during the present year, at least ten slavers have been fitted out in New York for one in the entire South."
(The South in the 1850's as Seen by British Consuls, Laura A. White, The Journal of Southern History, February 1935, excerpts, pp. 29, 31, 36-41)