During the Civil War, Darnestown saw no major battles but experienced major troop movements throughout the conflict. After Fort Sumter fell on April 14, 1861, and Lincoln called out 75,000 state militia on April 15 and 42,000 volunteers for three-year service on May 3, the 9th New York State Militia was in Darnestown in June 1861. Following the Union defeat at First Bull Run on July 21, 1861, Union General Banks and the Army of the Potomac arrived in Darnestown in August 1861. After the Union defeat at Ball's Bluff on October 21, 1861, Banks' troops moved from Darnestown to Frederick for winter quarters in December 1861, while detachments of the 19th Massachusetts Infantry performed provost duty there from December 1861 to March 1862. In September 1862, Union General William Franklin's VI Corps of General McClellan's Army of the Potomac moved through Darnestown to Antietam, where the Battle of Antietam Creek on September 17, 1862, became the bloodiest day of the Civil War. On June 27-28, 1863, Confederate Brigadier General Wade Hampton of J. E. B. Stuart's cavalry moved from Rower's Ford to Darnestown on the way to Rockville, shortly before the Battle of Gettysburg of July 1-3, 1863, the bloodiest battle of the war. During General Jubal Early's raid on Washington, D.C., on July 13, 1864, his retreating Confederate army passed through Darnestown on its way to Virginia, and on July 14, 1864, Union Major General Horatio Wright's VI Corps traveled through Darnestown in pursuit. The war ended with Lee's surrender to Grant at Appomattox on April 9, 1865.