The "Eastern Theater" refers to the primary area of military operations during the American Civil War, primarily located in the eastern United States. This region included key states such as Virginia, Maryland, and Pennsylvania, where significant battles like Gettysburg and Antietam took place. The Eastern Theater was characterized by its strategic importance and the presence of major armies, including the Union and Confederate forces. The Eastern Theater was marked by intense and often brutal combat, with notable military leaders such as General Robert E. Lee for the Confederacy and General Ulysses S. Grant for the Union. The outcomes of battles in this theater significantly influenced the overall course of the Civil War, shaping political and social dynamics in the nation.