On this day in history - July 1st, 1863 - the Battle of Gettysburg opens.
Gettysburg involved the most casualties of the American Civil War, and is half the turning point of the conflict (the other being the Battle of Vicksburg; Vicksburg surrendered one day after Gettysburg ended).
Confederate General Robert E. Lee attempted to invade Federal territory by marching north into Pennsylvania. General George Meade set up his defenses around Gettysburg including famous locations like Little Round Top, the Wheatfield and Devil's Den.
On the third day of the battle, the Confederates launched an assault known as Pickett's Charge against Federal forces holding Cemetery Ridge. In this engagement one can find "the High Water Mark of the Confederacy," the one place in Union lines where Pickett's Charge punched a hole.
Lee and the Confederacy never again launched such an attack on the Union for the rest of the war.