The United Kingdom of Great Britain and Ireland remained officially neutral throughout the American Civil War (1861–1865). It legally recognized the belligerent status of the Confederate States of America (CSA) but never recognized it as a nation and neither signed a treaty with it nor ever exchanged ambassadors. Over 90 percent of Confederate trade with Britain ended, causing a severe shortage of cotton by 1862. Private British blockade runners sent munitions and luxuries to Confederate ports in return for cotton and tobacco. In Manchester, the massive reduction of available American cotton caused an economic disaster referred to as the Lancashire Cotton Famine. Despite the high unemployment, some Manchester cotton workers refused out of principle to process any cotton from America, leading to direct praise from President Lincoln, whose statue in Manchester bears a plaque which quotes his appreciation for the textile workers in "helping abolish slavery". Top British officials debated offering to mediate in the first 18 months, which the Confederacy wanted but the United States strongly rejected.

William Henry Seward was an American politician who served as United States Secretary of State from 1861 to 1869, and earlier served as governor of New York and as a United States senator. A determined opponent of the spread of slavery in the years leading up to the American Civil War, he was a prominent figure in the Republican Party in its formative years, and was praised for his work on behalf of the Union as Secretary of State during the Civil War. He also negotiated the treaty for the United States to purchase the Alaska Territory.