When I left the new visitors' center, I decided to start the self-guided auto tour from Pleasanton Avenue, since I had already seen the Cemetery Hill portion by foot. The Pennsylvania Memorial (#12) is the first thing you see. You may actually park and start there if you turn on the little road before Hancock Avenue (which is one-way north). It was around 9 AM on a Friday morning but the Pennsylvania Memorial was already crowded and noisy, so I decided to head to the next stop which is the High Water Mark (#15) before most of the tour buses arrived.
Wikipedia tells us that the high-water mark of the Confederacy refers to a location on Cemetery Ridge. It is a symbolic reference to the arguably best chance the Confederate Army had of achieving victory in the war, not the farthest north that GEN Robert E. Lee's army had advanced geographically. On the third day of the battle at Gettysburg (July 3, 1863), GEN Lee ordered an attack on the Union center, located on Cemetery Ridge. This offensive maneuver called for almost 12,500 men to march over 1000 yards of dangerously open terrain. This became known as Pickett's Charge. The attack was unsuccessful even though Confederate troops briefly penetrated the Union line at what is now called "The Angle." Lee's Army of Northern Virginia retreated the next day, leaving Gettysburg for Virginia. Although the war lasted almost another two years, Lee launched few offensive operations during that time, none of them near the scale of the Gettysburg Campaign.