Which Civil War battle marked the bloodiest single day in American history with 25,000 casualties?

The Battle of Antietam, which took place on September 17, 1862, is recognized as the bloodiest single day in American history, resulting in approximately 25,000 casualties. This battle was significant not only for its high casualty rate but also for its strategic outcome. It marked a turning point in the Civil War, as it provided the Union with a much-needed victory. The battle also had far-reaching implications, as it prompted President Abraham Lincoln to issue the Emancipation Proclamation shortly afterward, shifting the war's focus toward the abolition of slavery.

The other battles listed, while important in their own right, did not reach the same level of single-day casualties as Antietam. The Battle of Gettysburg, although one of the largest and most notable battles, unfolded over three days and had a different context and impact on the war's progression.