The US Civil War put a damper on the trade volume for a period of time, it came back stronger afterwards.
So successful was the transition of slave labor into sharecropping and tenant farming during and after the war that cotton production actually expanded dramatically.
By 1870, American cotton farmers surpassed their previous harvest high, set in 1860. By 1877, they regained and surpassed their pre-war market share in Great Britain. By 1880 they exported more cotton than they had in 1860.
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https://www.politico.com/magazine/story/2015/01/civil-war-co...During the US Civil War cotton volumes went down and mills, mill workers in Lancashire and Cheshire experienced widespread poverty ...
However for a well placed elite few, cotton profits from trade climbed dramatically ..
Despite cotton shortages in England, merchants would sometimes re-export the materials that did arrive to other ports in Europe. Notably, they also re-exported materials from the South to the North, because the Union also struggled from being cut off from direct trade with the Confederacy. As a result, during the war, cotton grown in the Confederacy could be shipped out of a southern port to Britain to evade the Union blockade, sold in Liverpool, and then shipped back across the Atlantic to a northern port, evading the Confederate cruisers.
Liverpool's docks also benefitted as profitable wartime enterprises emerged, particularly the increased trade of commodities such as ships and armaments. The Union's merchant marine, nearly the world's largest in 1860, was devastated throughout the war in part by the Confederate warships supplied through Liverpool. In addition, as a result of the war, cotton speculation and brokerage, rather than trade in cotton itself, became immensely profitable for a number of merchants.
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https://ldhi.library.cofc.edu/exhibits/show/liverpools-aberc...Interesting; I was under the impression that the British just found new sources of cotton. From the American perspective this story is mostly told as a losing bet from the Confederate side—the South believed that Britain was so dependent on Southern cotton that they would intervene on their side of the war. Given the intensity of British public opinion against slavery this seems like a bad bet, but if the Confederates had better judgment they probably wouldn’t have started the war in the first place.
IIRC (I don't have historic trade complexity to hand, I once did for a project some years ago) the British did cultivate new sources (eg India) after experiencing a volume lull for some time.
Over a longer arc the cloth trade itself grew in volume and demand for raw fibre increased, absorbing the post Civil War US production again.
You're correct that public sentiment opposed slavery and that unionised mill workers in England supported a ban on non use of "slave cotton".
What also occurred, as often happens in war, is that a profitable black market trade grew and lined the pockets of many middle men, at the expense of growers who had reduced profits and embargos to deal with and for mill workers who saw less actual work as bale numbers plummeted.