The battle, one of the most influential of the war, marked the turning point for Union forces as Confederate general Robert E. Lee was forced to retreat to Virginia. Famed Civil War photographer Matthew Brady, who is often credited as the first photojournalist for his work during the war, photographed many of Lincoln's most well-known and enduring images.

Photo: President Lincoln stands proudly with Union troops following the Battle of Antietam in September 1862, in which 26,000 soldiers were killed or wounded.