This historical theme focuses on the epic struggle between the North and the South that eliminated both slavery and the right of secession as a consequential political theory. Included are all military, political, and diplomatic activities related to this first of the "total" American wars, and all other political and social activities of this era not related to the war.

Subthemes include the following aspects of the Civil War: The Nation Divides, 1860-1861; War in the East; War in the West; Naval Action; and Political and Diplomatic Scene.

Gettysburg National Military Park

Located 50 miles northwest of Baltimore, the small town of Gettysburg, Pennsylvania was the site of the largest Civil War battle ever waged in the Western Hemisphere. The Battle of Gettysburg opened on July 1, 1863 and closed two days later with the climactic "Pickett's Charge". It resulted in a Union victory for the Army of the Potomac which successfully turned back the second invasion of the North by General Robert E. Lee's Army of Northern Virginia. Over 51,000 soldiers were killed, wounded or captured making it the bloodiest battle of the Civil War. It was also a major turning point in the war. Historians have referred to the Battle of Gettysburg as the "High Water Mark of the Confederacy." It was the last major effort by Lee to take the fighting out of Virginia and into northern states.