Copperheads were during the American Civil War a term for persons in the North who opposed the war policy and supported restoration of the Union through a negotiated settlement with the South.
The term may be considered derogatory as it derives from the name of a venomous snake. However, self-proclaimed copperheads interpreted the term as referring to the head of Liberty on certain copper coins. An alternative term is Peace Democrats, as most, but not all, were Democrats.
Copperheads supposedly were involved in the "Knights of the Golden Circle", which successively became the "Order of American Knights" and the "Sons of Liberty". Although Republicans accused these groups of treasonable activities and used this as propaganda during the 1864 election, there is little evidence to support the accusation.