Northern Democratic critics of the Lincoln administration’s policy during the Civil War were known as Copperheads and were repeatedly linked to conspiracies to disrupt northern military operations and to help establish the independence of the Confederate States of America.

Named after the venomous snake, Copperheads were considered traitors to the Union and were accused by Republicans of creating a civil war within the Civil War. While many Democrats were critical of Republican policies pursued during the war, the vast majority of Democrats remained loyal to the Union cause.

Seeking partisan advantage at the polls, many Republican political leaders transformed Democratic criticism of the war into disloyalty. Associating the Democrats with such secret societies as the Knights of the Golden Circle, the Order of American Knights, and the Sons of Liberty, Republicans repeatedly linked the Democratic Party with alleged conspiracies to disrupt the war effort and permanently divide the nation.

Democratic dissent about Republican war policies was not fictitious. While Democrats had rallied to the flag in the aftermath of the firing on Fort Sumter, Republican policies on emancipation and civil liberties quickly raised doubts about the effect the war was having on U.S. society.

President Lincoln’s preliminary Emancipation Proclamation, issued shortly after the battle of Antietam, caused Democratic politicians and newspaper editors to vigorously criticize the administration’s war policies. Believing in the “Constitution as it is and the Union as it was,” leading Democratic politicians such as Ohio’s Clement Vallandigham and Indiana’s Daniel W. Voorhees charged that the war was now being waged for racial equality.

Democratic newspaper editors, such as Charles Lanphier of the Illinois State Register, Samuel Medary of the Columbus, Ohio, Crisis, and Wilbur Storey of the Chicago Times raised the issue of racial amalgamation along with the threat of economic displacement for white, particularly Irish, workers.

President Lincoln’s suspension of the writ of habeas corpus along with the arbitrary arrest and imprisonment of a few prominent Democrats, such as Dennis Mahoney, editor of the Dubuque, Iowa, Herald, raised fears that U.S. traditions of individual rights were being supplanted by military despotism.

Economic depression in the agricultural lower Midwest also fueled Democratic dissent. With the closing of the Mississippi River, traditional trading routes between the South and the lower Midwest were disrupted. Farmers now had to ship their product to market via the Great Lakes and northern railroads.

Rising railroad rates cut into agricultural profits and raised complaints that the interests of the farming Midwest were being sacrificed to northern capitalists. Combined with such measures as the Morrill Tariff, there emerged a robust western sectionalism, articulated by Vallandigham, Ohio’s Samuel “Sunset” Cox, Senator William A. Richardson of Illinois, and Daniel Voorhees, that was highly critical of “Puritan” New England and northern manufacturing interests.

From practically the war’s beginning, eager Republican newspaper editors and politicians attempted to profit from Democratic war criticism by painting the entire party as treasonous. One strategy was to accuse Democrats of membership in so-called secret or dark lantern societies. The alleged treasonous societies were the Knights of the Golden Circle (KGC), the Order of American Knights (OAK), and a reconstituted Sons of Liberty (SOL).

The Golden Circle was the invention of George W. L. Blickley, a no-account drifter born in Virginia who migrated to Cincinnati in the 1850s. The Order of American Knights was the brainchild of Phineas G. Wright, a New York native who was living in St. Louis when the Civil War erupted. Harrison Dodd, a respectable Indianapolis Democrat who felt Democrats needed to counteract Republican propaganda, founded the Sons of Liberty.

Republican newspaper editors, politicians, and Union military officers wildly exaggerated the membership in all of these organizations. For instance, through the skillful propagandizing of Republican governors Oliver Morton (Indiana) and Richard Yates (Illinois), the Knights of the Golden Circle was said to have thousands of members in Ohio, Indiana, and Illinois; yet hardly any actual local organizations were known to exist.

Similarly, as a result of an exposé written by John Sanderson, an aide to General William S. Rosecrans stationed in St. Louis, the Order of American Knights was portrayed as a mass organization with thousands of dedicated members. In reality, the OAK had a few, isolated cells (temples) located in the Midwest. Few, if any, prominent Democrats belonged to these shadowy organizations.

Unlike the Knights of the Golden Circle and the Order of American Knights, the Sons of Liberty had slightly more credible membership. Formed to counteract the Republican Union League, the Sons were modeled after the patriotic organization of the American Revolution. A number of prominent Democrats were associated with the Sons of Liberty including Clement Vallandigham and S. Corning Judd, a popular Illinois Democrat.

Concerned that constitutional liberty might be a casualty of the war, the main function of the Sons of Liberty was to protect republicanism from the excesses of civil war. Unfortunately the ill-timed actions of a few foolhardy Democrats along with the eager propagandizing of Republican publicists gave credibility to allegations of Democratic treason in such “plots” as the Northwest Confederacy and the Camp Douglas uprising.

Charges that Democratic conspirators were plotting to separate the Midwestern states from New England and form a Northwest Confederacy was a common charge against the Democrats during the war. Since 1864 was an election year, Republicans played up alleged plots of Democratic disloyalty for partisan gain. One Republican governor eager to seize opportunity was Oliver Morton of Indiana.

Using evidence gathered by Colonel Henry Carrington, Morton had a prominent group of Indiana Democrats—Harrison Dodd and seven associates— arrested and charged with treason. Eventually four Democrats—Lambdin P. Milligan, William Bowles, Stephen Horsey, and Andrew Humphrey—were tried before a military court (while charged, Dodd escaped and fled to Canada).

While Felix Stidger, a disreputable informant in the pay of Carrington, manufactured the majority of the evidence, the military tribunal nevertheless convicted the defendants and sentenced them to death. The Indianapolis treason trials gave Indiana Republicans a decided advantage in the fall campaign.

Similarly the so-called Camp Douglas conspiracy relied on manufactured evidence skillfully elicited by unsuspecting and, in some cases, unintelligent Democrats. The brainchild of Chicago Tribune president William Deacon Bross, the “Camp Douglas conspiracy” was the alleged attempt of local Democrats, aided and abetted by Confederate agents, to free thousands of Confederate prisoners of war held at Camp Douglas in Chicago.

The conspiracy theory grew and was nurtured by I. Winslow Ayers, a sleazy opportunist who hoped to profit from his untruthful allegations. Eventually over 100 Democrats were arrested in Chicago in late 1864. In a highly publicized treason trial conducted in Cincinnati in January 1865, only eight defendants were charged: George St. Leger Grenfell, Benjamin Anderson, Vincent Marmaduke, George Cantrell, Charles T. Daniel, Charles Walsh, Buckner Morris, and Richard T. Semmes. Tried before a military tribunal, only five of the defendants were convicted, and only one, St. Leger Grenfell, was sentenced to death.

In fact, no one convicted in any of the treason trials was executed. No doubt realizing the essential sham character of the trial, President Andrew Johnson eventually reduced death sentences to life imprisonment for the defendants of the Indianapolis treason trials—Milligan, Bowles, and Horseya suit filed by Milligan, on 3 April, the Supreme Court handed down ex parte Milligan, which denied the legitimacy of military tribunals when civilian courts were functioning.

The three defendants were subsequently released on 12 April 1866. Similarly, the Cincinnati Treason Trials defendants found a measure of vindication. Of the five convicted defendants, one committed suicide (Anderson) and one (Daniels) escaped.

Two defendants were eventually pardoned and St. Leger Grenfell’s death sentence was changed to life imprisonment. The actions of federal officials after the war were a candid acknowledgment of excesses committed in the name of patriotism during the war. (Humphrey had been freed earlier). In response to

For many years after the war, historians largely accepted the Republican verdict that the Democratic Party constituted a disloyal minority. While a few Democrats did belong to secret societies and openly supported the Confederacy, the vast majority were loyal supporters of the war and patriotic citizens. Opposed to emancipation and fiercely committed to constitutional liberties, most Copperheads were not conspirators but a respectable opposition party.