The 21st New York was in the thick of the Civil War in the Shenandoah Valley from January 1864 to the end of the war. The regiment fought against Confederate generals, guerrillas, and partisan rangers such as John Singleton Mosby. It fought in the Battle of New Market, accompanied David Hunter on his raid to Lynchburg, opposed Jubal Early in his 1864 Maryland offensive, and engaged in countless additional skirmishes in Virginia and West Virginia.