The Knights of the Golden Circle was a Texas-based secret society. Their objective was to create a confederation of slave-holding states in parts of Mexico and the West Indies, extending slavery; the group's plan thus mirrored the objectives of secession, a cause they actively supported during the Civil War. Legend has it that they hid the fabled confederate gold allegedly sent off for safe keeping as the waning days of the war. Others have linked them to the KKK.
At the link below is a fascinating history of the KGC and the historical context, it is after all subtitled "A History of Secession from 1834 to 1861." It was written by a member of the order and published in 1861. The rituals and degree structure described in this book clearly indicate the influence of Freemasonry; whether it was founded by men who happened to be Masons is unclear, as Freemasonry is not mentioned in the text.