The Battle of Gettysburg (July 1-3, 1863), fought in and around the town of Gettysburg, Pennsylvania, as part of the Gettysburg Campaign, was the battle with the largest number of casualties in the American Civil WarThe Battle of Antietam, the culmination of Lee's first invasion of the North, had the largest number of casualties in a single day, about 23,000. and is frequently cited as the war's turning point.Rawley, p. 147. Sauers, p. 827. McPherson, p. 665; McPherson cites the combination of Gettysburg and Vicksburg as the turning point. Union Maj. Gen. George Gordon Meade's Army of the Potomac defeated attacks by Confederate Gen. Robert E. Lee's Army of Northern Virginia, ending Lee's invasion of the North.

Following his success at Chancellorsville in May 1863, Lee led his army through the Shenandoah Valley for his second invasion of the North, hoping to reach as far as Harrisburg, Pennsylvania, or even Philadelphia, and to influence Northern politicians to give up their prosecution of the war. Prodded by President Abraham Lincoln, Maj. Gen. Joseph Hooker moved his army in pursuit, but was relieved just three days before the battle and replaced by Meade.

The two armies began to collide at Gettysburg on July 1, 1863, as Lee urgently concentrated his forces there. Low ridges to the northwest of town were defended initially by a Union cavalry division, which was soon reinforced with two corps of Union infantry. However, two large Confederate corps assaulted them from the northwest and north, collapsing the hastily developed Union lines, sending the defenders retreating through the streets of town to the hills just to the south.

On the second day of battle, most of both armies had assembled. The Union line was laid out in a defensive formation resembling a fishhook. Lee launched a heavy assault on the Union left flank, and fierce fighting raged at Little Round Top, the Wheatfield, Devil's Den, and the Peach Orchard. On the Union right, demonstrations escalated into full-scale assaults on Culp's Hill and Cemetery Hill. Across the battlefield, despite significant losses, the Union defenders held their lines.

On the third day of battle, July 3, fighting resumed on Culp's Hill, and cavalry battles raged to the east and south, but the main event was a dramatic infantry assault by 12,500 Confederates against the center of the Union line on Cemetery Ridge. Pickett's Charge was repulsed by Union rifle and artillery fire at great losses to the Confederate army. Lee led his army on a torturous retreat back to Virginia. Between 46,000 and 51,000 Americans were casualties in the three-day battle. That November, President Lincoln used the dedication ceremony for the Gettysburg National Cemetery to honor the fallen and redefine the purpose of the war in his historic Gettysburg Address.

The Gettysburg Address is one of the most famous speeches by U.S. President Abraham Lincoln and one of the most quoted speeches in United States history.Historian James McPherson has called it "The most eloquent expression of the new birth of freedom brought forth by reform liberalism.", in McPherson, James M. Drawn with the Sword: Reflections on the American Civil War Oxford: Oxford University Press, 1996. p. 185. Google Book Search. Retrieved on November 27, 2007. It was delivered at the dedication of the Soldiers' National Cemetery in Gettysburg, Pennsylvania, on the afternoon of Thursday, November 19, 1863, during the American Civil War, four and a half months after the Union armies defeated those of the Confederacy at the decisive Battle of Gettysburg.

Abraham Lincoln's carefully crafted address, secondary to other presentations that day, came to be regarded as one of the greatest speeches in American history. In just over two minutes, Lincoln invoked the principles of human equality espoused by the Declaration of Independence and redefined the Civil War as a struggle not merely for the Union, but as "a new birth of freedom" that would bring true equality to all of its citizens, and that would also create a unified nation in which states' rights were no longer dominant.

Beginning with the now-iconic phrase "Four score and seven years ago...", Lincoln referred to the events of the Civil War and described the ceremony at Gettysburg as an opportunity not only to consecrate the grounds of a cemetery, but also to dedicate the living to the struggle to ensure that "government of the people, by the people, for the people, shall not perish from the earth".

Category: Image - :Lincolnatgettysburg.jpg|thumb|right|300px|The only confirmed photo of Abraham Lincoln at Gettysburg (seated), taken about noon, just after Lincoln arrived and some three hours before he spoke. To Lincoln's right is his bodyguard, Ward Hill Lamon.

Despite the speech's prominent place in the history and popular culture of the United States, the exact wording of the speech is disputed. The five known manuscripts of the Gettysburg Address differ in a number of details and also differ from contemporary newspaper reprints of the speech.