The battle that took place on September 17, 1862, represented the first major defeat for Lee's Army of Northern Virginia in the North, effectively halting Confederate advances.

By thwarting the invasion, the Union not only safeguarded Northern territories but also altered the course of the war. This strategic triumph enabled President Lincoln to issue the Emancipation Proclamation, which redefined the war's objectives and rallied support for the Union cause, thereby enhancing its importance in the broader conflict.