2. Battle of Antietam (1862)

On September 17, 1862, near the quiet Maryland town of Sharpsburg, Union and Confederate forces collided in what would become the bloodiest single-day battle in American history. The relentless fighting at Antietam resulted in nearly 23,000 casualties, a sobering testament to the war’s brutal intensity. Though tactically inconclusive, the Union army’s resilience halted General Lee’s initial invasion of northern territory, providing President Lincoln the political opportunity he needed. Shortly thereafter, Lincoln issued the Emancipation Proclamation, transforming the war’s purpose by declaring all enslaved persons in Confederate-held territories forever free, a landmark step toward ending slavery in America.