Idaho in the American Civil War Idaho in the American Civil War The history of Idaho in the American Civil War is atypical, as the territory was far from the battlefields. At the start of the Civil War, modern-day Idaho was part of the Washington Territory. On March 3, 1863, the Idaho Territory was formed, consisting of the entirety of modern-day Idaho, Montana, and all but southwest Wyoming. However, there were concerns about Confederate sympathizers in the eastern half of the territory, in what is present-day Montana. As a result, in 1863 Sidney Edgerton traveled quickly to see President Abraham Lincoln about the situation; this was
Western Theater of the American Civil War formally surrendered his force on May 9. Wilson's cavalry officially took control of Tallahassee, Florida, on May 20, the last Confederate state capital east of the Mississippi to be captured, completing the Western Theater operations. A detachment of Wilson's cavalry captured Confederate President Jefferson Davis on May 10 near Irwinville, Georgia. The costliest land battles in the western theater, measured by casualties (killed, wounded, captured, and missing), were: Western Theater of the American Civil War The Western Theater of the American Civil War encompassed major military operations in the states of Alabama, Georgia, Florida, Mississippi, North Carolina, Kentucky, South Carolina