- See Civil War for more examples.
The American Civil War was a conflict fought in the United States on Earth during the mid-19th century between the United States, also known as the Union, and a group of southern states, which asserted their independence from the United States and formed the Confederate States of America. The war ended in a United States victory. After the war the former Confederate states were eventually reassimilated into the Union. The war was eventually seen as one of the key events in bringing about an eventual end to slavery and oppression on Earth. (VOY episode: "The Q and the Grey")
The following June, during Major General William T. Sherman's March to the Sea, the Battle of Pine Mountain was fought near Pine Mountain, Georgia. One of the United States Army units at the battle was the 102nd New York Infantry Regiment, commanded by Colonel Thaddius Riker. Riker was wounded during the battle, but he was carried to safety by one of his soldiers. Over 500 years later it was discovered that the soldier who saved Riker's life was the member of the Q Continuum who came to be known as Quinn. (VOY episode: "Death Wish")
Ancestors of a number of prominent Starfleet officers fought in the American Civil War. Commander Tracy Dane's ancestors fought in the United States Army, and began a trend of military service in the Dane family that would continue for over 400 years. (TOS novel: The Captain's Daughter) Captain William T. Riker was a descendant of Colonel Thaddius Riker of the 102nd New York Infantry Regiment. (VOY episode: "The Q and the Grey") Geordi La Forge had an ancestor who fought in the Battle of the Crater on July 30, 1864 with the US 28th Colored Troops out of Indiana. (TNG novel: The Forgotten War)
Jonathan Archer witnessed a scene from the American Civil War while the timeline realigned itself after Archer's crew repaired damage done to it during the Temporal Cold War. (ENT episode: "Storm Front")
When the Q fought their own civil war, Q chose to represent the war by using an illusion of the American Civil War, in the hopes that the crew of the USS Voyager could comprehend the Continuum and the war they were fighting. (VOY episode: "The Q and the Grey")
In 2276, Leonard McCoy, a native of Georgia, referred to the American Civil War as the "War Between the States" and the "Late Great Unpleasantness" during his Right of Statement. (TOS novel: The Romulan Way)