Willem van de Velde the Younger, Dutch ships in a calm. Public domain.
Lincoln blockaded Southern ports so the Confederacy could not freely sell cotton or buy arms.
A poor household in the Confederacy faced shortages as salt, medicine, and cloth stopped arriving.
A middling southern household that had lived on store-bought goods saw coffee and tools turn scarce and dear.
Planters who had counted on London lost their market, while a few blockade runners risked ships for very high profits.
On April 19, 1861, Lincoln proclaimed a blockade from South Carolina to Texas, and he extended it as more states left the Union.
The cordon was thin in the first seasons and much harder to slip later in the war.
Britain did not break it to rescue the cotton trade.
Proclamation of Blockade, April 19, 1861; James M. McPherson, Battle Cry of Freedom (1988)