American Civil War
The American Civil War was a major conflict conducted in the United States from 1861 to 1865. According to the Second Doctor, it was also called the War Between the States and had, in part, to do with slavery. As the Doctor once told a disinterested Zoe Heriot, "The Southern states had Negro slaves. In the Northern states, owning slaves was outlawed. The North wanted the South to free its slaves, so the Southern states tried to leave the Union." (PROSE: Doctor Who and the War Games)
According to Southern states like South Carolina, however, the issue was less about slavery specifically and more about the power individual states had relative to the Federal government in Washington, D.C.. South Carolina made their precise legal position known in a formal legal document which they issued prior to leaving the Federal Union. (PROSE: Blood and Hope)
Over the course of his lifetimes, the Doctor had a few encounters with this American conflict.
The War Lords kidnapped several American Civil War soldiers for the War Games to which the Second Doctor, Jamie McCrimmon and Zoe Heriot were subjected. (TV: The War Games)
On 23 December 1861, the Fifth Doctor and Turlough assisted Mrs Elkins in defending her Virginia farmhouse from a group of deserters led by Lucius Casler. (PROSE: Comforts of Home)
The Third Doctor and Charlie Fisher visited Gettysburg in 1863 and aided the Union Army in winning the battle there. (COMIC: Backtime)
The Fifth Doctor later visited the United States in the company of Peri Brown and Erimem during the last few months of the war. During this period, the Doctor acted as a physician for both sides, and ultimately prevented the premature assassination of U.S. President Abraham Lincoln in Richmond, Virginia on 9 April 1865. The would-be assassin was Aaron Eddowes. (PROSE: Blood and Hope) Only a few days later, on 14 April 1865, the Sixth Doctor and Evelyn Smythe would become embroiled in a plot to prevent Lincoln from being assassinated by John Wilkes Booth in Ford's Theatre in Washington, D.C.. (AUDIO: Assassin in the Limelight)
Conversely, the renegade Time Lasy Berenyi claimed credit for designing what seemed to be Lincoln's assassination. (PROSE: Untitled)
In the parallel universe where Earth had been devastated by the effects of the Inferno Project, the South won the war — thus America was referred to as the American Confederation instead of the United States. (PROSE: The Face of the Enemy)