Lambdin Purdy Milligan (March 24, 1812 – December 21, 1899) was a lawyer and farmer who was known for his extreme opinions on states' rights and his opposition to the Abraham Lincoln administration's conduct of the American Civil War. Believing that the Confederate states of the South had the power under the U.S. Constitution to secede from the Union, he opposed the war to reunite the nation. Milligan became a leader of the secret Order of American Knights (formerly the Knights of the Golden Circle, and later the Sons of Liberty, and advocated violent revolution against the U.S. government. U.S. Army forces arrested him at his home and tried him and other conspirators by military commission for disloyalty and conspiracy. Found guilty, he was sentenced to death. A habeas corpus appeal made its way from the federal circuit court in Indianapolis to the U.S. Supreme Court, which in 1866 ruled that the application of military tribunals to citizens when civil courts are open and operating was unconstitutional. See Ex parte Milligan 71 U.S. (4 Wall.) 2 (1866). Following the Court's ruling on April 3, 1866, Milligan and the others were released from custody. He returned home and practiced law in Huntington, Indiana, where he later filed a civil suit claiming damages for the military arrest and trial. On May 30, 1871, the jury found in Milligan's favor, but federal and state statutes limited the award for damages to five dollars plus court costs.
Milligan, who was of Irish descent, was born on a farm near Saint Clairsville, in Kirkwood Township, Belmont County, Ohio. His parents were Moses Milligan Sr, a soldier in the American Revolutionary War, and Mary (née Purday) Milligan. Lambdin was the eighth of nine siblings.