The Knights of the Golden Circle was an organization that existed in the United States from the 1850s through the 1860s which espoused the idea of a radical expansion, and realignment, of the United States into an extremely “pro-slavery” nation. Their major goal was to promote the idea of the seizure, as part of Manifest Destiny, of additional territory for the United States in Cuba, Mexico, Central America, and the Caribbean, with the ultimate goal being that each of these new territories be added to the United States as “slave states” – those allowing slavery. This planned goal also aimed at potentially creating a new super-Confederacy of states/republics, if necessary, encompassing the Southern states in the United States and the other new territories, with a capital centered in Havana, Cuba.
Now this new nation, (shown above in green), would have represented a major investment of military and cultural power by the United States to be achieved and probably was beyond the immediate capacity of the nation in the 1850s. However the idea had many adherents in the American South and southern portions of middle states, mainly due to the economic possibilities it presented and concerns about the growing power of abolitionism as a political force in the United States. The Knights of the Golden Circle were strongly pro-Southern as regional tensions increased in the United States and the organization supported the seceding states in 1861. Many Democrats in the northern United States during the Civil War expressed support for some ideas purported by the Knights of the Golden Circle and members of the organization took part in some early military actions by the growing Confederate forces.
The organization had less real impact during the American Civil War but it was a lightening rod for Northern concerns about Southern sympathizers acting as spies and saboteurs during the Civil War. Members of the Knights of the Golden Circle were regularly targeted for arrest by United States law enforcement and its key leaders were expelled from northern territory when caught. The image of the Knights of the Golden Circle in the United States as traitors was not helped by activities like the attempting to outfit a secret privateer boat in California to attack Pacific shipping by the United States. The organization did not survive the defeat of the southern states in the American Civil War and its membership most likely dissolved after the war.
I say “most likely” because the Knights of the Golden Circle have become one of the darlings of conspiracy theorists who posit the group survived the end of the American Civil War and became a key player in efforts to prepare for a second American Civil War. Such theories are grounded mostly in speculation than anything solid, but it does give the organization a lasting minor place even in modern United States history.