The final day's fighting was clearly a Union victory. For this, Lee must ultimately bear a large share of the responsibility, perhaps all of it. Despite the heroic way in which the troops conducted the day's attack, it had been an unwise, possibly even a foregone conclusion. The battle had been lost on the second day, when, despite horrendous losses, the Union army had attained the security of Cemetery Ridge. Lee ought to have heeded Longstreet's advice and avoided a direct clash entirely. To have attempted a frontal assault against superior forces was at best foolhardy, given the numerous demonstrations of the superiority of the defense over the offense which had occurred throughout the entire war. Barely six months earlier the Army of the Potomac had itself essayed a frontal assault at Fredericksburg only to be repulsed at great cost with but trivial losses to the Confederacy. On July 3 Meade held a somewhat less favorable position than Lee had held at Fredericksburg, but with substantially more men. The best course of action for July 3 would have been to pull Ewell's corps back over on the left and stand defense along Seminary Ridge, tempting Meade into an attack. Had Meade made such an effort, the result could well have been a Union debacle. And if he failed to attack, or tried to engage in some fancy maneuvers, Lee could pull his army back across a series of readily defensible ridge-lines until he could break off contact and retire.
In the Army of the Potomac it seems that everyone did well. Meade, who after all had only been in command five days, kept his head, lightly supervising his subordinates, all of whom where doing their jobs properly, and moved his reserves as he saw the need develop. The true hero of the day was undoubtedly Hancock, who was constantly at the post of danger and did exactly what had to be done to break Lee's grand attack.