"recent devious part in the Civil War"

The American Civil War was waged between 1861 and 1865, and originally sparked by attempts by the southern states of America to leave the union of states.  During the war, Britain remained ostensibly neutral, even as British shipmakers supplied vessels to the southern, Confederate side, and the British government privately considered officially recognising the Confederacy as the legitimate government.  Neither of these actions would have been popular in northern, Yankee areas like Boston.