General Lee made his worst mistake. He ordered an attack against Cemetery Ridge. This battle is better known as Pickett's Charge. It it one of the biggest failures in history.
Lee's plan was to march from Seminary Ridge and charge up the slope of Cemetery Ridge. Thirteen thousand men would make the march. General George Pickett of Longstreet's First Corps was to be in charge. Hill's Third Corps would join the charge. Longstreet argued with Lee that the charge would not work but Lee wouldn’t listen.
A little after 1pm, 140 Confederate cannons started shooting at Cemetery Ridge. It was a four mile line of guns from Seminary Ridge to the Peach Orchard. For two hours, the guns roared. Many of the shells over shot the Union troops. Pickett started his charge around 3pm. Twenty-three cannons, 500 gunners, and some 57 hundred Union soldiers attacked. Only a small number of Rebels made it to the top of the ridge. The charge lasted one hour. Half the Confederates that started the charge did not come back. The Union losses were much smaller.