Antie'tam (ăn-tē' tam), a creek in Maryland, where was fought one of the great battles of the Civil War, September 17, 1862, between the Union army, with 57,614 men in the field, under General McClellan, and the Confederate, with 38,000 men, under General Lee. The battle raged with great slaughter from early morning until dark. The result was not decisive, the Union loss being over 11,000 and the Confederate loss about 10,000. McClellan did not renew the attack, and on the 18th Lee retreated in safety. But the moral effect was to encourage the north, and on the strength of Antietam President Lincoln issued his proclamation abolishing slavery.